added ability to use preprocessor functions in all modules, component and plugins (anywhere in php, js, css, xml files)

#if premium
...
#endif

or
#if free
...
#endif

What is supported If / Else if:
#if DEFINITION : succeeds if DEFINITION is set and is true (in the PHP way)
#ifdef DEFINITION : succeeds if DEFINITION is set
#ifndef DEFINITION : succeeds if DEFINITION is not set
#elif DEFINITION
#elifdef DEFINITION
#elifndef DEFINITION
#endif