Fix broken check for id3lib UTF-16 bug

https://bugzilla.gnome.org/show_bug.cgi?id=729328
Update translation list for Windows installer
Added Korean translation
Add Korean to the translation list
Avoid a crash when browsing hidden directories

If viewing hidden directories is disabled, EasyTAG will fail to find a
hidden path in the directory model, and will crash when trying to
retrieve the full path from the model. Avoid this by returning early
from Browser_Tree_Select_Dir().

https://bugzilla.gnome.org/show_bug.cgi?id=730326
Add .m4v as a supported extension for MP4 tags

https://bugzilla.gnome.org/show_bug.cgi?id=730421
Refactor Browser_List_Refresh_File_In_List()

Simplify iterations over the tree model.
Correctly restore disabled process fields options

https://bugzilla.gnome.org/show_bug.cgi?id=730573
Add Nautilus actions extension

Include a context menu item for opening directories, and one for opening
supported files, in a Nautilus extension.

https://bugzilla.gnome.org/show_bug.cgi?id=731493
Minor improvements to the Nautilus extension

Document the requirements for the extension in the README. Add a
COPYING.GPL3, as including the license is a requirement. Update
.gitignore for new files.
Use type definition macro for Nautilus extension

Use G_DEFINE_DYNAMIC_TYPE_EXTENDED for the Nautilus extension, and move
all the code into a single file as a consequence.
Initialize gettext in Nautilus extension startup
Add generated help translations to .gitignore
Update British English translation
Updated Greek translation
Updated Brazilian Portuguese translation
Updated Spanish translation
Updated Spanish Translation
Updated Polish translation
Fixed a few crashes because of dangling pointers

The two list stores from the artist/album view contain pointers to the
list in ETCore->ETArtistAlbumFileList. When the complete list was freed,
the GUI still used the pointers in the list stores and crashed.

I saw segmentation faults while toggling between artist/album and
directory view and furthermore while shutting down EasyTAG.