Create a new independant ContextDataPart with a tree and columns to
display local values, context functions and parent context values
injected using this context.
Add icons on tree nodes in ContextDataPart.
Manage context function : value is the real value computed (if possible)
and the tooltip contains now the context function name
Manage the tree on Context Data columns
Fix the search. The inherited values injected using context node was not
taken into account. Now you can search for 'org.eclipse.ui.selection'
and all the nodes where it is used are displayed in blue.
Clean the code and fix some bugs. Ready to be merged in master branch.