Rename InsetXXX::contextMenu to InsetXXX::contextMenuName. Now this function doesn...

Rename InsetXXX::contextMenu to InsetXXX::contextMenuName. Now this function doesn't need all the parameters and we split the functionality of choosing which context menu to return, from the functionality of supplying the name for the Inset itself. Now, the InsetText context menu is returned for InsetCollapsables when the button is not hit by the mouse. There is no (intended) change in functionality for insets without a button, collapsed insets. This fixes partly bug #6642. A fix for InsetTabular and for insets with no button will follow.

git-svn-id: svn://svn.lyx.org/lyx/lyx-devel/trunk@36604 a592a061-630c-0410-9148-cb99ea01b6c8