Select the 'custom triggers' pane when adding new triggers

Fixes #1848
If you selected a non-editable trigger set (e.g. iTunes) then tried to add a trigger QS would crash
Fix a crash during startup

Setting the activation hotkey before QS had properly finished launching can cause problems
esp. when trying to change input sources
Merge pull request #1860 from quicksilver/crashFixes

Crash fixes