fixes #1, admin changes for piwik proxy #3.

fixes #1 - new PiwikTracker.php file for HTTP_REFERRER undefined error.
WIP admin changes for #3 piwik proxy script.
changed some variables to align code/database/language naming.
update of javascript method, changes for issue #3
changed javascript code to use '_paq.push' method.
javascript changes to resolve #3.
moved piwik-proxy file to opencart root.
changes for issue #3

added save of the settings to the piwik-proxy.php file.
corrected spelling mistake in admin area
vqmod wildcard for improved custom theme use
preparation for v0.4 release

readme edits