Making JSON-RPC accept more content types

According to the RFC for JSON-RPC over HTTP at
http://www.jsonrpc.org/historical/json-rpc-over-http.html
"Content-Type SHOULD be 'application/json-rpc' but MAY be
'application/json' or 'application/jsonrequest'"

This patch fixes HTTPJsonRpcHandler to allow for any of those three
content types when accepting JSON-RPC HTTP requests.

This also fixes compatibility with the popular Python library jsonrpclib
which uses the application/json-rpc content type.
[codegenerator] Helper.groovy: fix typo
[codegenerator] Helper.groovy: add support for class variables
[codegenerator] python: extend IN typemap to support int, double and float
renderer: replace render buffer indices with queues
renderer: simplify code by always maintaining one front buffer
renderer: remove now pointless GetNext(Decode/Render) function
renderer: name present buffer structure to be able to reference it
renderer: store bypass format in rendermanager instead

The present method will be overwritten on each flippage
renderer: drop copies of variables, use queue data directly
renderer: grab presentlock in AddVideoPicture
DVDAudioCodecFFmpeg: Grow the resampling buffer as needed instead of allocating it an arbitrary big size.
DVDAudioCodecFFmpeg: Remove write only assignment.
DllAvFilter: Always include libavfilter/buffersrc.h for av_buffersrc_add_frame.
Revert "Merge pull request #2809 from jmarshallnz/no_skip_for_you"

This reverts commit c5a85f72b6f685be832d4e3a43328de49baabf03, reversing
changes made to e9aed1d645158647aa2006ac4b2d2d18a3d1ecbf.
Only allow prev-next chapter jumps outside of active playlist
Move player action handling out of GUIDialogVideoOSD and GUIWindowFullScreen into Application
Merge pull request #2855 from Voyager1/skip-chapters-withoutplaylist

Re-enable skip previous/next as chapter jumps, when outside of playlist context
[codegenerator] python: extend swig template to support class variables
[legacy] hide C++ only public class variables from swig