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/zh_CN/LC_MESSAGES/ui.po

@@ -9,26 +9,6 @@ msgstr ""
 "Language: zh_CN\n"
 "Plural-Forms: nplurals=1; plural=0;\n"
 
-#: cocoa/inter/app.py:15 qt/base/app.py:38
-msgid "Scanning for duplicates"
-msgstr "重复文件扫描中"
-
-#: cocoa/inter/app.py:16 qt/base/app.py:39
-msgid "Loading"
-msgstr "载入中"
-
-#: cocoa/inter/app.py:17 qt/base/app.py:40
-msgid "Moving"
-msgstr "移动中"
-
-#: cocoa/inter/app.py:18 qt/base/app.py:41
-msgid "Copying"
-msgstr "复制中"
-
-#: cocoa/inter/app.py:19
-msgid "Sending to Trash"
-msgstr "移到垃圾桶"
-
 #: cocoa/inter/app_me.py:34
 msgid "Removing dead tracks from your iTunes Library"
 msgstr "从你的iTunes库中移除无效的音轨"
@@ -81,10 +61,6 @@ msgstr ""
 msgid "The iPhoto application couldn't be found."
 msgstr "The iPhoto application couldn't be found."
 
-#: qt/base/app.py:42
-msgid "Sending files to the recycle bin"
-msgstr "将文件移到回收站"
-
 #: qt/base/app.py:95
 msgid "Quit"
 msgstr "退出"
@@ -118,12 +94,6 @@ msgstr "检查更新"
 msgid "Open Debug Log"
 msgstr "打开调试记录"
 
-#: qt/base/app.py:217 cocoa/base/en.lproj/Localizable.strings:0
-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 "目前还有任务在执行，新任务无法开启。请等待几秒钟后再重新试一次。"
-
 #: qt/base/app.py:257
 msgid "{} file (*.{})"
 msgstr ""
@@ -854,9 +824,3 @@ msgstr "Zoom"
 #: qt/base/deletion_options.py:46
 msgid " (unsupported)"
 msgstr ""
-
-#~ msgid " (Mac OS X or Linux only)"
-#~ msgstr ""
-
-#~ msgid "Re-Prioritize Results"
-#~ msgstr "Re-Prioritize Results"