Issue #31 and some bugfixes
bugfix for NPE on save pdf issue
check state of CommandButton with attached popup

CommandButtons with popup were not correctly disabled when according
action's isEnabled() method returned false
Merge remote-tracking branch 'origin/master' into ribbons

Conflicts:
	docear_plugin_pdfutilities/src/org/docear/plugin/pdfutilities/PdfUtilitiesController.java