qt: merge ME edition into SE

(breaks PE temporarily)

Adds a Standard/Music Application Mode button to SE and thus adds the
ability to run ME scan types in SE. When in Music mode, the
Music-specific results window, details panel and preferences panel will
show up.

All preferences except scan_type become shared between app modes
(changing the pref in a mode changes it in the other mode).

Results Window and Details Panel are now re-created at each scan
operation because they could change their type between two runs.

Preferences panel is instantiated on the fly and discarded after close.

This is a very big merge operation and I'm trying to touch as little
code as possible, sometimes at the cost of elegance. I try to minimize
the breakage that this change brings.

qt/se/preferences_dialog.py

@@ -13,6 +13,7 @@ from hscommon.plat import ISWINDOWS, ISLINUX
 from hscommon.trans import trget
 from hscommon.util import tryint
 
+from core.app import AppMode
 from core.scanner import ScanType
 
 from ..base.preferences_dialog import PreferencesDialogBase
@@ -81,7 +82,7 @@ class PreferencesDialog(PreferencesDialogBase):
         self.sizeThresholdEdit.setText(str(prefs.small_file_threshold))
 
         # Update UI state based on selected scan type
-        scan_type = prefs.scan_type
+        scan_type = prefs.get_scan_type(AppMode.Standard)
         word_based = scan_type == ScanType.Filename
         self.filterHardnessSlider.setEnabled(word_based)
         self.matchSimilarBox.setEnabled(word_based)