Fix rendering of source icons in playlist view on retina OS X 10.9
In the tag editor, make the reset button appear on the left side for RTL text; #2673
Add the ability to choose destination folder in the transcoder dialog.
Test for string length
Formatting
Add mp2 to the list of extensions shown in the files tab.  Fixes #4103
Make is_rtl()/set_rtl() methods private
Remove trailing semicolon
playlist context menu entry: Show in library
Use isEmpty() instead of length()
Both cases move the clear button to the same position
Adjust the ui and clean up code.

The selection of a destination folder is now done by pressing the button 'Select...'.
The last selected folders along with the option 'Alongside the originals' are
available in the box 'destination'.

The methods TranscodeDialog::TrimPath and TranscodeDialog::GetOutputFileName are now
const.

Minor formatting fixes.
Merge pull request #4107 from goetzc/master

playlist context menu entry: Show in library.  Fixes #1162
Merge pull request #4102 from Tatsh/fix-edittagdialog-rtl

In the tag editor, make the reset button appear on the left side for RTL
Fixes #2673
Merge pull request #4105 from paperbagcorner/transcoderdestination

Add the ability to choose destination folder in the transcoder dialog.  Fixes #2776.