Fix index out of range unandled exception when request.postpath is an empty list

verified HEAD works, but Twisted rejects OPTIONS and PATCH, not sure why, need to follow up with kaosat after his merge

updated the merge from kaosat-dev to remove jsonpickle (for now) and fix some subtle bugs that broke existing BDDs

- added automatic handling of 501 NotImplemented error in case a url
exists but the specific requested method does not .
For simplicity, this is done via an added dict called "urlMethods" in
RequestRouter, that maps urls to lists of implemented http methods , and
is filled in_registerRouters

- added support for json serialization using jsonpickle 

- moved convertToJson to convert module

- removed forced content type setting in __generateResponse that
sets MediaType.TEXT_PLAIN as content type, when response is a string :
it should be set exclusively based on what the caller can accept/ has
asked for, as specified in the docstring for this method

- fixed bug that would mangle routed urls after passing more than once
in __registerRouters : this is visible when running unit tests or any
other situation when a RestResource is recreated with the same
"service"

bug fixes: handle conversions of numerics in JSON responses, better parsing of arguments with unexpected characters