shadowbox 6.x-3.1

Changes since DRUPAL-6--3-0:

• #556656 by derjochenmeyer and aacraig: Fix uninitialized variables.
• Default to en language.
• Moving check for third party software.
• Better name for function.
• Improve docs.
• Adding some basic comments to _add_js and _add_css calls.
• Added SHADOWBOX_DEFAULT_PATH.
• Removing lots of lines from the module's docs in favour of linking to official docs.
• More work on the docs.
• Missing SHADOWBOX_DEFAULT_PATH.
• More work on the docs.
• #566074 by shp: Fix automatic image handling.
• Added ability to specify, per content type and per field, the source of the text to use for the title attribute and therefore the overlay text.