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
remove duplicate -rpcsslciphers help message from init
Merge pull request #3129 from Diapolo/rem-dup-helpmsg

remove duplicate -rpcsslciphers help message from init
Add test for monetary value formatting

Tests for issue #3126.
This problem pops up after upgrading json-spirit.
Merge pull request #3133 from laanwj/2013_10_format_monetary_test

Add test for monetary value formatting
Add test for monetary value parsing

Just-in-case sanity test for JSON spirit and AmountFromValue.
Also update rpc_format_monetary_values test to use ValueFromAmount,
so that ValueFromAmount is also tested.
Merge pull request #3134 from laanwj/2013_10_format_monetary_test

Add test for monetary value parsing
bitcoingui: show main window (if hidden) on modal messages
RPC: error code changes and prevent crash with walletpassphrase

- fix crash with walletpassphrase by checking if RPC server is running and
  give a friendly error message how to fix this (fixes #3100)
- add 3 new RPCErrorCodes RPC_SERVER_NOT_STARTED, RPC_NODE_ALREADY_ADDED
  and RCP_NODE_NOT_ADDED (I checked the source to not use a number already
  in use for RPC_SERVER_NOT_STARTED)
- use the new codes where needed / missing
- add missing use of RPC_INVALID_PARAMETER
[Qt]: fix num Blocks to maturity in Tx description

- as we have main.h included in transactiondesc.cpp, we now also use
  COINBASE_MATURITY +  1 for the descriptive string
- fixes #3131
Merge pull request #3137 from Diapolo/RPC

RPC: error code changes and prevent crash with walletpassphrase
Merge pull request #3139 from Diapolo/maturity

[Qt]: fix num Blocks to maturity in Tx description
Merge pull request #3135 from Diapolo/bitcoingui

bitcoingui: show main window (if hidden) on modal messages