added index tree view and placeholder for commit message
setup the stage and worktree views using QSortFilterModel
removed visibility control from the WorkingTree… items as this is controlled by the WorkingTreeFilteModel.
don't hide "stateless" items (namely directories) from the tree view
added WTF_Staged and the appropriate filter checkboxes
use the WTF_Staged flag within the work tree model
replaced WTF_… filter with Git::Status
added basic actions for staging / unstaring file changes
added class for stage tree view and basic frame for the context menu action slots
initialize file item members
removed unused member mModel
added method deeplyMapToSource() to treeviews to handle filtered model indices
cleanup constructors
added indexToItem() converter method to working tree model
override setModel() in tree views
correctly map and check the model indices;
plus corrections to display the ctx-menu and minor formatting changes
assert on null working tree item
corrected a type cast
added safety to item casting within working tree model
recurse into sort/filter models