Code style / syntax cleanup #2

http://joomlacode.org/gf/project/joomla/tracker/?action=TrackerItemEdit&tracker_item_id=31323

These are code style and minor syntax changes. So nothing in functionality should be changed.

This PR is the 2nd in a series.

This is a cleanup of the following folders:

/administrator/components/com_categories
/administrator/components/com_checkin
/administrator/components/com_config

administrator/templates/hathor/html/com_categories
administrator/templates/hathor/html/com_checkin
/administrator/templates/hathor/html/com_config

#### Testing instructions
Check if all the views of these components still function as expected.

#### PR Series
1. https://github.com/joomla/joomla-cms/pull/1395
2. https://github.com/joomla/joomla-cms/pull/1403