Updated Thai translation
plugins: move zeitgeist to gedit-plugins project

Reference: https://bugzilla.gnome.org/show_bug.cgi?id=731799
Signed-off-by: Igor Gnatenko <i.gnatenko.brain@gmail.com>
document: add missing g_free

Adding a missing g_free for short_name in
finalize method ( thanks to weld for
having found it )
Use GtkSourceEncoding in GeditEncoding
Move encoding utils functions to gedit-utils

gedit-encodings will be removed, but the utils functions will still be
needed in gedit.
encodings-dialog: use GtkSourceEncoding
encodings-combo-box: use GtkSourceEncoding
app: use GtkSourceEncoding
io-error-info-bar: use GtkSourceEncoding
commands: use GtkSourceEncoding
window: use GtkSourceEncoding
file-chooser-dialog: use GtkSourceEncoding
tab: use GtkSourceEncoding
Add gedit_document_get_file()

The function returns the associated GtkSourceFile.
Port GeditDocument and GeditTab to GtkSourceFile (not finished)