Refactor Scan_Convert_P20_Into_Space()

https://bugzilla.gnome.org/show_bug.cgi?id=726108
Set default size on image properties dialogue

This gives a better result than setting a size request on the image
types tree view.
Added Telugu initial Translation
Update supported format list in help
Add help page on ID3 tag version problems

Also see https://bugs.launchpad.net/ubuntu/+source/easytag/+bug/684352
Use C++ TagLib API for MP4 tags

Eventually, this will enable handling of cover art and extended tags for
MP4 files.
Support extended fields for MP4 tags

Support the extended tags that are supported by TagLib, including total
track number, disc number (and total), composer, copyright and encoded
by.

https://bugzilla.gnome.org/show_bug.cgi?id=701506
Add G_DECL boilerplate to picture.h

The new taglib C++ reader needs to use picture.h from C++ source, add
G_BEGIN_DECLS and G_END_DECLS for correct symbol naming.
Implement cover art support for MP4

Adds support for saving cover image into MP4 files, and show the images
tab for them as well.

https://bugzilla.gnome.org/show_bug.cgi?id=701506
Support album artist in MP4 files

Use the atom directly, rather than going through the properties
convenience API.
Use C++ TagLib API for MP4 header information
Add GIO/TagLib compatibility layer

Create GIO based implementations of TagLib::IOStream, so TagLib can be used
over GIO. The implementation still lacks almost all error handling, but works
in normal situations.
Clean up GIO TagLib wrapper

Conform better with EasyTAG coding style.
Use GIO wrappers in mp4_tag.cc

Make mp4_tag.cc use GIO wrapper for reading and writing MP4 tags with
TagLib.
Use GIO wrappers in mp4_header.cc
Detect good set of warning flags for C++ compiler

At least gcc's g++ does not like all warning flags that the C compiler
does, so try them separately. Use -Werror to get failures, as the wrong
flags only cause a warning.
Improve error handling in GIO/TagLib wrapper

Add some error checks and a method for getting the error to the
GIO/TagLib compatibility layer.
Add basic error reporting to mp4_tag.cc

Add some error reporting enabled by updates in GIO wrapper to
mp4_tag.cc.
Add basic error reporting to mp4_header.cc

Add some error reporting enabled by updates in GIO wrapper to
mp4_header.cc.
Remove auto pointer template

Additionally, unref the stream on destruction of GIO_InputStream, as
closing the stream is not sufficient.