Fixes for issues #15 #16 #17 #19

Fixed Issue #15 Race condition that broke folder menu items after reconnection to the btsync agent
Fixes Issue #16 Menuitem "Enable Debug Logging": fixed initial state and added state refresh.
Fixes Issue #17 Add support for new function PAUSE/RESUME (rudimental)
Fixed Issue #19 In case of disconnection/error, only the folder menu items will be deleted. Some menu items will be disabled.