Get rid of filename extensions completely.
Now use exceptions alot more than error status (allows cleaning up code).
Adds the filter_##_name syntax which allows calling the same filter multiple times.
Adds a simple transparency filter.
Adds a simple untransparent filter.
Rewrites the rounded corners filter.
Rewrites the resize to fit filter (again).
Rewrites the rotate filter.
Fixes problems with empty cache path
alt attribute is now allowed to be empty.