[btcsuite/btcd] d26aaf: Create `generate` RPC command to close #362

[Alex Akselrod]

  Branch: refs/heads/master
  Home:   https://github.com/btcsuite/btcd
  Commit: d26aaffb2b8989705045481d489e3f3f830234b3
      
https://github.com/btcsuite/btcd/commit/d26aaffb2b8989705045481d489e3f3f830234b3
  Author: Alex Akselrod <a...@akselrod.org>
  Date:   2015-05-04 (Mon, 04 May 2015)

  Changed paths:
    M btcjson/btcdextcmds.go
    M btcjson/btcdextcmds_test.go
    M chaincfg/params.go
    M cpuminer.go
    M docs/json_rpc_api.md
    M rpcserver.go
    M rpcserverhelp.go

  Log Message:
  -----------
  Create `generate` RPC command to close #362

Create GenerateCmd in btcjson v2. Update tests to check GenerateCmd.

Update chaincfg/params.go with a new bool in Params, GenerateSupported,
with true values in SimNetParams and RegressionNetParams and false in
the others.

Create new flag, discreteMining, in CPUMiner struct.

Add GenerateNBlocks function to cpuminer.go and handleGenerate
function to rpcserver.go.

Update documentation for the RPC calls.