icon-canvas-item: attempt to fix up a11y for CajaIconCanvasItem

https://git.gnome.org/browse/nautilus/commit/?h=gnome-3-0&id=184096f912b119edde1f538e8cdd5ea593d753ca
Possible solution for x-caja-desktop issue
Remove ConsoleKit usage

Closes https://github.com/mate-desktop/caja/issues/125
Closes https://github.com/mate-desktop/caja/issues/226
Show trash in tree panel

Closes https://github.com/mate-desktop/caja/issues/233

Also unused commented code in fm-tree-view.c
replace g_free call on GFile objects, fixes #196
Fix minor man page issues, closes #280

Patch by Mike Gabriel <mike.gabriel@das-netzwerkteam.de>