Modernized progress window GUI

Following the refactoring that has been initiated in pdfmasher's
"vala" branch, I pushed more progress window logic into the
core.

The UI code is now a bit dumber than it used to be, and the core
now directly decides when the progress window is shown and
hidden. The "job finished" notification is also directly sent by the
core. Job description update logic is handled by a core gui
textfield.

Job description contsants also moved to the core, triggering
a localisation migration from "ui" to "core".

locale/it/LC_MESSAGES/core.po

@@ -9,55 +9,55 @@ msgstr ""
 "Language: it\n"
 "Plural-Forms: nplurals=2; plural=(n != 1);\n"
 
-#: core/app.py:37
+#: core/app.py:40
 msgid "There are no marked duplicates. Nothing has been done."
 msgstr ""
 
-#: core/app.py:38
+#: core/app.py:41
 msgid "There are no selected duplicates. Nothing has been done."
 msgstr ""
 
-#: core/app.py:39
+#: core/app.py:42
 msgid ""
 "You're about to open many files at once. Depending on what those files are "
 "opened with, doing so can create quite a mess. Continue?"
 msgstr ""
 
-#: core/app.py:98
+#: core/app.py:110
 msgid "will only be able to delete, move or copy 10 duplicates at once"
 msgstr ""
 
-#: core/app.py:232
+#: core/app.py:254
 msgid "No duplicates found."
 msgstr "Non sono stati trovati dei duplicati."
 
-#: core/app.py:245
+#: core/app.py:267
 msgid "All marked files were copied successfully."
 msgstr "Tutti i file marcati sono stati copiati correttamente."
 
-#: core/app.py:246
+#: core/app.py:268
 msgid "All marked files were moved successfully."
 msgstr "Tutti i file marcati sono stati spostati correttamente."
 
-#: core/app.py:247
+#: core/app.py:269
 msgid "All marked files were successfully sent to Trash."
 msgstr "Tutti i file marcati sono stati inviati nel cestino."
 
-#: core/app.py:274
+#: core/app.py:296
 msgid ""
 "You cannot delete, move or copy more than 10 duplicates at once in demo "
 "mode."
 msgstr ""
 
-#: core/app.py:285
+#: core/app.py:307
 msgid "'{}' already is in the list."
 msgstr "'{}' è già nella lista."
 
-#: core/app.py:287
+#: core/app.py:309
 msgid "'{}' does not exist."
 msgstr "'{}' non esiste."
 
-#: core/app.py:294
+#: core/app.py:316
 msgid ""
 "All selected %d matches are going to be ignored in all subsequent scans. "
 "Continue?"
@@ -65,45 +65,45 @@ msgstr ""
 "Tutti i %d elementi che coincidono verranno ignorati in tutte le scansioni "
 "successive. Continuare?"
 
-#: core/app.py:354
+#: core/app.py:376
 msgid "copy"
 msgstr ""
 
-#: core/app.py:354
+#: core/app.py:376
 msgid "move"
 msgstr ""
 
-#: core/app.py:355
+#: core/app.py:377
 msgid "Select a directory to {} marked files to"
 msgstr ""
 
-#: core/app.py:381
+#: core/app.py:403
 msgid "Select a destination for your exported CSV"
 msgstr ""
 
-#: core/app.py:406
+#: core/app.py:428
 msgid "You have no custom command set up. Set it up in your preferences."
 msgstr ""
 "Non hai impostato nessun comando personalizzato. Impostalo nelle tue "
 "preferenze."
 
-#: core/app.py:512 core/app.py:523
+#: core/app.py:535 core/app.py:546
 msgid "You are about to remove %d files from results. Continue?"
 msgstr "Stai per rimuovere %d file dai risultati. Continuare?"
 
-#: core/app.py:543
+#: core/app.py:566
 msgid "{} duplicate groups were changed by the re-prioritization."
 msgstr ""
 
-#: core/app.py:563
+#: core/app.py:586
 msgid "Collecting files to scan"
 msgstr "Raccolta file da scansionare"
 
-#: core/app.py:574
+#: core/app.py:597
 msgid "The selected directories contain no scannable file."
 msgstr "Le cartelle selezionate non contengono file da scansionare."
 
-#: core/app.py:613
+#: core/app.py:636
 msgid "%s (%d discarded)"
 msgstr "%s (%d scartati)"
 
@@ -213,3 +213,35 @@ msgstr "Verificate %d/%d somiglianze"
 #: core_pe/matchexif.py:18
 msgid "Read EXIF of %d/%d pictures"
 msgstr ""
+
+#: core/app.py:58
+msgid "Scanning for duplicates"
+msgstr "Scansione per i duplicati"
+
+#: core/app.py:59
+msgid "Loading"
+msgstr "Caricamento"
+
+#: core/app.py:60
+msgid "Moving"
+msgstr "Spostamento"
+
+#: core/app.py:61
+msgid "Copying"
+msgstr "Copia in corso"
+
+#: core/app.py:62
+msgid "Sending to Trash"
+msgstr "Spostamento nel cestino"
+
+#: core/app.py:65
+msgid "Sending files to the recycle bin"
+msgstr "Spostamento nel cestino"
+
+#: core/app.py:246
+msgid ""
+"A previous action is still hanging in there. You can't start a new one yet. "
+"Wait a few seconds, then try again."
+msgstr ""
+"Un'azione precedente è ancora in corso. Non puoi cominciarne una nuova. "
+"Aspetta qualche secondo e quindi riprova."