implemented missing actions for help ribbon

the ribbon xml files are !!not!! up-to-date yet
actions for the "Tools and Settings" task

the ribbon description xml file is !!!not!!! included yet
Issue #28: impl. as new part of the docear pdf inspector
made sure to close the PdfExtractor
ToggleRibbonAction (min-/maximize ribbon)

thank you Dimitry :)
save backups for link conversions and some refactoring
Issue #55
Merge remote-tracking branch 'origin/master' into ribbons

Conflicts:
	docear_plugin_core/resources/core.properties