*Title: New 'ezmodule' template operator.

*Documentation:
New 'ezmodule' template operator checks module (or view) is enabled
or not basing on Rules settings which are set under [SiteAccessRules]
section of the 'settings/site.ini' file.
Syntax:
{ezmodule( uri )}

If passed string as uri parameter contains uri to enabled module (or view)
then the operator returns true, otherwise it returns false.
Note, the operator doesn't check access permissions to a module functions
or views per user, this can be checked only by using 'content/access'
template fetch function.
Example:

{def $isTipafriendEnabled = ezmodule( 'content/tipafriend' )}
{if $isTipafriendEnabled}
<a href={'content/tipafriend/187'|ezurl()}>Click to tip this to your friend</a>
{/if}
{undef}