Allow the 'current context' AppleScript property to work with multiple-context

Created a new method 'currentContextAsString' to either fetch from
currentContextPath or compute a string by joining activeContexts.
small fix to avoid an edge case
for any ActionWithString type action set the description equal to the parameter, closes #341
open prefs window when ControlPlane is launched while running, closes
adds ConnectBluetoothDevice action from clundie, closes #333
Merge pull request #328 from waisbrot/applescript-fix

Allow 'current context' to work in AppleScript when multiple contexts are enabled