* introduce grin_keychain, encapsulate derivation of secret_keys
* core compiles against keychain, tests don't run yet
* core tests are now passing against keychain
* wip - getting wallet working with keychain
* add util and keychain to travis test matrix
* basic test around key derivation
* Adding output stats from plugin, when available
* adding grin config
* moving pow crate from core/pow to it's own crate
* moving POW/mining stuff into pow module, and removing mining dependency from chain
* refactored most of mining into pow module...miner.rs still in server
* update grin tests
* updating genesis block mining to use configured miner, if available
* chain tests back into chain, done with pow refactor
* use tag of cuckoo-miner for pr
* playing around with changing cuckoo sizes on the fly
* modifying tests to use global cuckoo parameters, and checking results
* check for pow size
* Changing global function names, and removing length from POW serialization
Block, Output and Kernel now have bitmasks to hold supported
features and eventually versioning. Will make adding features and
updates easier and open the possibility of soft forks.
First added feature for Output and Kernel is the marking of coinbase
related ones. Allows the validation of the coinbase part of a block.
