v1.2.0

1. web3js compatibility. With v1.2 user can connect their favorite tools in the
   Ethereum eco-system (such as Metamask, Subgraph) to IoTeX blockchain simply by
   setting up RPC endpoint to IoTeX endpoint
2. Support multiple chain DB files. v1.2 will now generate 1 db file for every
   1,000,000 accumulated blocks added to the blockchain. This prevents one single
   overly large db file in the long run, and opens up possibility for faster and
   incremental download (only need to download new latest db files)
3. Reduced DB file size. Together with the multiple DB files feature, the DB file
   itself has been overhaualed by using an improved block storage with better
   compression. The estimated storage saving is about 30~40% when enabling v1.2
4. Added EVM revert message in transaction receipt. For contract calls that get
   reverted in the middle, we can now see the actual revert error message from the
   transaction receipt
5. Improved transaction indexing scheme. As a result, certain API queries (for
   example, pull all transactions from an address within a block range) now get a
   much faster response
6. Improved p2p connection reliability and network robustness
7. Fix ioctl crashes in Ubuntu when creating an action