[Tizen] Fix invalid AttributeFilter.attributeName issue

AttributeFilter has been refactored.
Setter and getter for attributeName have been added.

BUG=XWALK-3122

Change-Id: I5507a67731371846a6f86860117f3fef29ae1ef8
Remove unused variables in file media_renderer.cc

Variables "objects" and "child" of type GVariant* were declared but never used.
That's why they were removed. Some other nits were fixed.
Merge pull request #417 from sstolinski/XWALK_3122

[Tizen] Fix invalid AttributeFilter.attributeName issue
Merge pull request #418 from piotrowskim/rm_unused_media_renderer

Remove unused variables in file media_renderer.cc
Bump version to 0.131
master update to upstream