adding reset to staged items in the commit dialog

should fix #2254
fixed keyboard shortcut "R" for both Unstaged/Staged lists
#2294 fixed: Commit dialog hangs for hours on selecting or deselecting many files
updated to use _currentFileList
Merge pull request #2307 from bookman25/reset_staged_file

Reset staged file
Correction of list of branches display 2 times in combobox

The list of branch is feed in InitToolStripBranchFilter() and also
in UpdateBranchFilterItems() but filtered if needed.
Remove first call to prevent displaying of branches twice that
happens due to an Async call...
Merge pull request #2324 from pmiossec/correct_list_branches

Correction of list of branches display 2 times in branches combobox
Fix missing space when calling fetch --tags
Merge pull request #2326 from w3dman/fix-fetch-tags

Fix missing space when calling fetch --tags