Tidy up rpc module:
* Move directory up to ripple/module/rpc
* Use C++11 idioms and best practices
Better types and more comments in RippleCalc.

* Better automatic conversions to and from tagged uint160 varints.
* Start using tagged variants of uint160 for Currency, Account.
* Comments from 2014/6/11 RippleCalc session.
Add missing beast includes
Tidy up overlay declarations

Conflicts:
	src/ripple/module/app/main/Application.cpp
	src/ripple/module/app/misc/NetworkOPs.cpp
	src/ripple/module/app/peers/PeerSet.cpp
Use strand::running_in_this_thread instead of bool
Move overlay up one directory

Conflicts:
	src/ripple/module/app/main/Application.cpp
	src/ripple/module/app/misc/NetworkOPs.cpp
	src/ripple/module/app/peers/PeerSet.cpp
	src/ripple/overlay/impl/PeerDoor.cpp
Remove unused protocol message types:
* mtACCOUNT
* mtCONTACT
* mtERROR
* mtGET_ACCOUNT
* mtGET_CONTACTS
* mtGET_VALIDATIONS
* mtSEARCH_TRANSACTION
* mtUNUSED_FIELD
Update README.md
Add abstract_protocol_handler, message_stream
[FOLD] Add member to PeerImp
[FOLD] Route data through message_stream
[WIP]
[FOLD] Move mtHELLO rule enforcement
[FOLD] cut mtHELLO over to abstract_protocol_handler
Add peer_protocol_detector
Add hooks for LoadEvent in message_stream
Move remainder of message handlers
Use new read path