Changed exception for invalid postion/offset from EasyRdf_Exception to InvalidArgumentException
Added throwing of OutOfBoundsException if the position in EasyRdf_Container::seek() does not exist
Bumped up version number to 0.8.0-beta.2
Added optimisation for calling EasyRdf_Graph->resources() multiple times
Changed return variable name in EasyRdf_Graph::all() to make it more obvious what is going on..
Made passing a URI to delete() behave more like all() and get() - you must enclose in <> now (fixes #126)