Methods for returning the result as raw image streams

getResultAsPNG(), getResultAsJPG(), getResultAsGIF() return a merged resource image as a raw image stream (a string) which can be saved into a file or served on the fly by printing the result with the proper headers.
Don't allow $quality go below 99 on getTresultAsPNG()
PHPDoc

Fixed some bad phpdocs. There are still a lot of phpdoc fixes required.
Merge remote-tracking branch 'origin/phpdoc'