Second milestone done:
- libwallet_api split from libwallet (saves a lot of time when debugging...)
- misc build fixes for various configs (ie, readline not found, etc)
- fix for wallet side default setting of ring size (introduced when changing mixin to ring size)
- wallet2 now tries to minimize the number of tx creation calls when making a tx (mostly useful for ledger)
- monerod now warns when the disk space is low (also available via RPC)
- the wallet can now relay a tx it was previously created, but not sent (via RPC)
- reorg of dependencies (mostly for the wallet, and to try and keep build times down)
- some wallet refresh optimizations
- C port of the java PoC for bulletproofs by sarang