* Move CSS definitions to resources
* Add Gtk::Builder helpers
* Switch StatsDialog to Gtk::Builder
* Switch RelocateDialog to Gtk::Builder
* Switch OptionsDialog to Gtk::Builder
* Switch MakeDialog to Gtk::Builder
* Switch FilterBar to Gtk::Builder
* Switch MainWindow to Gtk::Builder
* Switch MessageLogWindow to Gtk::Builder
* Switch DetailsDialog to Gtk::Builder
* Switch PrefsDialog to Gtk::Builder
* Fixup translatable strings
Since this branch was brewing for a while, changes happened in the meantime.
The torrent list hotkeys include `CTR + A` and were always active,
swallowing text edit hotkeys in the filter entry.
Now they are only active when the torrent list is focused.
* (C++) Macros should not be used to define constants
* (C++) Memory should not be managed manually
* (C++) "void*" should not be used in typedefs, member variables, function parameters or return type
* (C++) When the "Rule-of-Zero" is not applicable, the "Rule-of-Five" should be followed
* (C++) "switch" statements should have "default" clauses
* (C++) "explicit" should be used on single-parameter constructors and conversiosn operators
* (C++) Non-const global variables should not be used
