Debugger: Enable/disable debug button

The debug button should be enabled or disabled after
checking if the project can be run in DebugMode.

Change-Id: I2700c1de290f89bae9456319c2e93857374838ed
Reviewed-by: hjk <hjk121@nokiamail.com>
Reviewed-by: Eike Ziller <eike.ziller@digia.com>