Updated Galician translations
Fix deprecated gtk+ margin left and right

_left is replaced by _start
_right is replaced by _end
Updated Russian translation
Fix usage of margins

Commit 4a33712cc740c8456284da03b13b329c7b6f780c replaced deprecated
-left and -right with -start and -end, but forgot to remove the LTR
check in one place.
docs: updated shortcut keys page to use new expanded syntax
view: release ref to the buffer in dispose()

This commit simplifies the code, there is no need for destroy() and
finalize(). dispose() is enough. References should be released in
dispose().
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.
Remove file loading and saving unit tests

The unit tests are in GtkSourceView.
GeditDocument: make load and save functions private

Make the following functions private:
gedit_document_load
gedit_document_load_stream
gedit_document_load_cancel
gedit_document_save
gedit_document_save_as

They are normally not needed by plugins. What plugins need is to do some
stuff before/after a file loading or saving, i.e. the following signals
are needed: "load", "loaded", "save", "saved".

By making the above functions private, it'll be easier to port
GeditDocument and GeditTab to GtkSourceFile.
Port to GtkSourceFileLoader