wx GUI: Fix bug
wx GUI: Improve textarea code
wx GUI: Add focus text area menu action
wx GUI: create_accelerator_table static method
wx GUI: Don't process Tab in the editor text area by default

Addresses #352
wx GUI: Allow properly disabling single extended accelerators
wx DBsearch: Improve code
wx GUI: Shortcuts for selecting the last notebook tabs
wx GUI: Maintain focus on logs when cycling if they had it
wx Tasklist: store snooze submenus in menu attributes
wx GUI: Reorganize default menu accelerators
wx GUI: Simplify code