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.

core_me/app.py

@@ -1,41 +0,0 @@
-# Copyright 2016 Hardcoded Software (http://www.hardcoded.net)
-#
-# This software is licensed under the "GPLv3" License as described in the "LICENSE" file,
-# which should be included with this package. The terms are also available at
-# http://www.gnu.org/licenses/gpl-3.0.html
-
-from core.app import DupeGuru as DupeGuruBase
-from . import prioritize
-from . import __appname__
-from . import scanner, fs
-from .result_table import ResultTable
-
-class DupeGuru(DupeGuruBase):
-    NAME = __appname__
-    METADATA_TO_READ = [
-        'size', 'mtime', 'duration', 'bitrate', 'samplerate', 'title', 'artist',
-        'album', 'genre', 'year', 'track', 'comment'
-    ]
-    SCANNER_CLASS = scanner.ScannerME
-
-    def __init__(self, view):
-        DupeGuruBase.__init__(self, view)
-        self.fileclasses = [fs.MusicFile]
-
-    def _get_dupe_sort_key(self, dupe, get_group, key, delta):
-        if key == 'folder_path':
-            dupe_folder_path = getattr(dupe, 'display_folder_path', dupe.folder_path)
-            return str(dupe_folder_path).lower()
-        return DupeGuruBase._get_dupe_sort_key(self, dupe, get_group, key, delta)
-
-    def _get_group_sort_key(self, group, key):
-        if key == 'folder_path':
-            dupe_folder_path = getattr(group.ref, 'display_folder_path', group.ref.folder_path)
-            return str(dupe_folder_path).lower()
-        return DupeGuruBase._get_group_sort_key(self, group, key)
-
-    def _prioritization_categories(self):
-        return prioritize.all_categories()
-
-    def _create_result_table(self):
-        return ResultTable(self)