Incorporated latest translatewiki changes and made minor improvements:
- Added Arabic (now complete) to index.
- Replaced Wikipedia http links with https using command line:
  sed -i 's/\(http\)\(:.*wikipedia\)/\1s\2/g' apps/*.soy apps/*/*.soy
- Improved message documentation for increment block.

Review URL: https://codereview.appspot.com/35920045

git-svn-id: http://blockly.googlecode.com/svn/trunk@1541 c400ca83-b69d-9dd7-9705-49c6b8615e23