genesis: add support for arbitrary initial height (#5191)

Adds a genesis parameter `initial_height` which specifies the initial block height, as well as ABCI `RequestInitChain.InitialHeight` to pass it to the ABCI application, and `State.InitialHeight` to keep track of the initial height throughout the code. Fixes #2543, based on [RFC-002](https://github.com/tendermint/spec/pull/119). Spec changes in https://github.com/tendermint/spec/pull/135.

config/toml.go

@@ -476,6 +476,7 @@ func ResetTestRootWithChainID(testName string, chainID string) *Config {
 var testGenesisFmt = `{
   "genesis_time": "2018-10-10T08:20:13.695936996Z",
   "chain_id": "%s",
+  "initial_height": "1",
   "validators": [
     {
       "pub_key": {