Sqlchain

Made API modules config selectable or Insight compatible if none set. Now a supplied API can be customized and integrated by editing the config file. This makes it easier to build web apps that need specific API calls. sqlchain-config adds all 5 supplied APIs by default. If upgrading you may need to edit the config file to add ones you use.

New config option called max_blks that limits how many blocks are kept in SQL db. This is useful when you primarily want to process realtime or not very old data. Used with a pruning node it indexes address/tx data back as far as max_blks, which is something you cannot do on a pruned node normally as txindex cannot be used. It also means you can start from a given block (set block in config) and not have to sync SQL db from Genesis; this allows a quick start up in some cases. Also fixed bugs in sync api.

New stuff:
- bech32
- multi coin support (tested with Dogecoin, Reddcoin, Litecoin, Vertcoin)
- sqchain-config (for setup/install now requires dialog package for curses interface)
- pylint support (to help find bugs)
- initial unit tests added (uses pytest, see README in tests dir)
- supports MySQL DB engines (tested with RocksDB and TokuDB)
- ZMQ support for bitcoind (instead of polling for tx/block updates)
- complete revision of DB schema (for segwit/bech32 and more block info)
- many bugs fixed