* Simplify scrypt constants with const block
* Add key store constructors and make their types private
* Simplify key store and file namings to be less Java Enterprise™
* Change test error logging to use t.Error(err)
* Reduce number of naked returns (just like my ex-gf)
* Simplify file reading path code
* Add new generic key_store interface
* Add new plaintext key store storing unprotected keys on disk
* Add new encrypted key store storing encrypted keys on disk
* Add new entropy mixing function using OS and go runtime sources