Store: add method stubs for array and file IO.
Helper: added module for small helper functions
CacheStore: implement file and array methods
RestStore: dummy implementations for file and array methods
setup.py: remove fcache from requirements
setup.py: remove simplejson from requirements
setup.py: add odml to requirements
CacheStore: implement file and array methods
helper.py:  change default prefix for random_str()
BasicStore: signature changed for set_file() and set_array()
RestStore: dummy implementations for file and array handling.
CachingRestStore: methods for files and arrays.
ResultDriver: build native objects with array data (untested)
CachingRestStore: fixed bug in __get_arraydata()
Merge branch 'stoewer' into development

Implementation of array and datafile handling in store classes and
the in result driver. The rest result implementation is still a dummy.