PHP Classes refactor & Cache improvments

Include all #312 cacheFixes branch with other improvements. 

## Main changes:
 * Use Pimple (http://pimple.sensiolabs.org/) as a shared container that initiate our classes.
 * Inject different dependencies (classes) to other classes
 * Separated KalturaResultObject into: Request Helper, Client Helper, Utility Helper, Cache Helper
 * Use Kaltura Cache Wrappers ( we now have the ability to change cache engine from file system to memcache in one line )
 * Make the use of globals as little as possible ( some of them moved into our $container )
 * Cache the playerConfig array
 * Use entry caching headers for our Iframe headers

Please review and merge