Add separate bitcoin-rpc client

This adds an executable `bitcoin-rpc` that only serves as a Bitcoin RPC
client.
The commit does not remove RPC functionality from the `bitcoind` yet,
this functionality should be deprecated but is left for a later version
to give users some time to switch.
Prettify some /Contrib READMEs

SYN

Remove Dead Readme-Qt Links.
Revert "Switch to using raw_utf8"

This reverts commit 2ecb7555a9df1e843fd25f588819e4ca1d94b266.
Revert "JSON Spirit updated to v4.06"

This reverts commit 2227389fa8fa1b9ff19234838fc7b641e935125b.
Merge pull request #3082 from laanwj/2013_10_rpccli3

Add separate bitcoin-rpc client
Merge pull request #3127 from jgarzik/smells-like-json-spirit

Revert recent json-spirit changes
Merge pull request #3123 from super3/master

Prettify some /Contrib READMEs