added maxCache option to AnnotationDB, and applied it to sliceAnnotation(). Now only items() and values() actually force loading of the full dataset into cache.
added maxCache option to AnnotationDB, and applied it to sliceAnnotation().
Now only items() and values() actually force loading of the full dataset into cache.

cjlee112/pygr,ctb/pygr,ctb/pygr,cjlee112/pygr,theoryno3/pygr,ctb/pygr,ctb/pygr,theoryno3/pygr,RitwikGupta/pygr,GenDataPro/pygr,cjlee112/pygr,cjlee112/pygr,RitwikGupta/pygr,theoryno3/pygr,ctb/pygr,GenDataPro/pygr,GenDataPro/pygr,RitwikGupta/pygr