Added MusicBrainz dialog

Added libmusicbrainz compilation flags
Added musicbrainz_dialog.ui containing MusicBrainz Dialog
Added new file mbentityview.c containing EtMbEntityView widget
MusicBrainz Search has been added to Toolbar and Menubar
show-musicbrainz is the action name
on_show_musicbrainz is the action callback
Implemented EtMbEntityView.

Modified musicbrainz_dialog.ui to create place for EtMbEntityView in the dialog
Implemented different functions of EtMbEntityView in mbentityview.c
Added EtMbEntityView in dialog in musicbrainz_dialog.c
Implemented Asynchronous Manual Search

Created a base library for MusicBrainz search in mb_search.c & mb_search.h
Implemented manual search functions in musicbrainz_dialog.c
Added support for displaying information about Mb5Entity in mbentityview.c
Implemented Select All, Unselect All Buttons. Added Artists and Type for Releases.

Added buttons in musicbrainz_dialog.ui
Added callbacks for buttons in musicbrainz_dialog.c
Added functions for above features in mbentityview.c
Added Red Line support in mbentityview.c and mb_search.c
Implemented Invert Selection and Toggle Red Lines

Added buttons for Invert Selection and Toggle Red Lines in musicbrainz_dialog.ui
Added callback functions for above buttons in musicbrainz_dialog.c
Used GtkFilterTreeModel for Toggle Red Lines in mbentityview.c
Added functions for Toggle Red Lines & Invert Selection in mbentityview.c
Implemented selection Up and Down

Added buttons for Up and Down in musicbrainz_dialog.ui
Added functions for above features in mbentityview.c & mbentityview.h
Added callbacks for functions in musicbrainz_dialog.c
Added more verbos Status Bar Messages and comments

Added function et_show_status_msg_in_idle to show messages in Status Bar in a thread safe manner
Added more messages depicting more information
Make TreeView multi selectable

Modified GtkTreeView in EtMbEntityView to select more than one rows.
Implemented Cancellation of Manual Search using GCancellable

Added various cancellation checks in all the modified files
Created a new GCancellable and pass it to every GSimpleResult thread function
Added a Stop button to allow cancellation
Double clicking on Red Line will give already downloaded results

Show the already downloaded stored results instead of redownloading them everytime.
Coding Style Improvements
Removed FIXME. Added some more comments
Implemented Search Selected Files

Added selected_find_thread_func which will search over all selected albums
Added selected_find_callback responsible for displaying the results.
Similar to Manual Search
Removed Trailing Whitespaces
Implement DiscID Search

Added support for searching DiscID in mb_search.c
Added dependency for libdiscid in configure.ac
Added support for displaying DiscID Search results in mbentityview.c
Added DiscID search's callback and thread_func in musicbrainz_dialog.c
Added Test for MusicBrainz Search

Added "make test" in Makefile.am
Added tests cases for MusicBrainz search in test-musicbrainz.c
Added a test soup-server in test-musicbrainz_server.c
Added different xml files containing MusicBrainz retrieved data for server
Coding Style Improvements and Converted Strings to Translatable Strings
Merged MusicBrainz test server and client into one file

Client and MusicBrainz test server are merged into one file test-musicbrainz.c
Added DiscID test
Use MB_ENTITY_KIND

Change MB_ENTITY_TYPE_* to MB_ENTITY_KIND_*
Made libmusicbrainz optional and added Close button

Made libmusicbrainz support optional in confiure.ac
Added Close Button