ChinaList is deprecated and has been replaced by Easylist China

Fixes #1516
Preferences: Prevent opening more than one window
Use open() instead of exec() in all dialogs

Avoid blocking exec().

Closes #1515
Mac: Open new window when clicking on Dock icon

Closes #1517
OpenSearchEngine: Use Json class instead QScriptEngine to parse suggestions
Fixed "Open blank tab" on new tab option on OS/2
Set default window size to be desktop size / 1.3
Save geometry of Preferences window

Closes #1514
Use desktop availableGeometry for default window size calculation
Qt5: Enable HighDPI pixmaps
SpellCheck: Fix loading dictionaries after user saves the spellcheck dialog
Updated empty.ts