* 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
* Adding cuckoo-miner into grin as a proper dependency now
* Defaulting to using cuckoo-miner
* Updates to tests to use cuckoo_miner by default, (using cuckoo16)
* Refactoring to allow for different miner implementations. Added conditional support for compiling and loading the cuckoo-miner plugin project.
* Small changes to experimentally integrate with cuckoo-miner and compatibility with latest version of cuckoo-miner.
* Turning off inclusion of cuckoo_miner by default
* Disabling simulate_parallel_mining test for now
* core: cleanup slicing impls for Hash
* core: clean up Readable trait, implement Readable/Writeable for various integers
* core: change Hash debug output to hex
* core: correct warnings in all modules
