Support for the Gaia Theme.

The Gaia theme applys defaults to button tags, that we want to ignore. Make
the css more specific so that the Gaia Theme will not override the look of
icons.
Allow users to search for nothing without an error.
Support for when Clean URL's is disabled.

Image paths can't use the 'q' parameter they must be absolute for apache to
serve them.
Hide the search results popup using a fade.

Bug in the use of "this" in a new context.
Reset tag level CSS rules set by BookReader.css
Center the display of search progress modal dialog box.

Previously it wasn't be centered for sites whose theme did not make the content
section of the site positioned relatively.
Merge pull request #5 from nigelgbanks/7.x-bug-fixes

7.x bug fixes