The `patricia_trie` crate is generic over the hasher (by way of HashDB) and node encoding scheme. Adds a new `patricia_trie_ethereum` crate with concrete impls for Keccak/RLP.
* Update `add_license` script
* run script
* add `remove duplicate lines script` and run it
* Revert changes `English spaces`
* strip whitespaces
* Revert `GPL` in files with `apache/mit license`
* don't append `gpl license` in files with other lic
* Don't append `gpl header` in files with other lic.
* re-ran script
* include c and cpp files too
* remove duplicate header
* rebase nit
* WIP
* Convert Ethcore error to use error_chain
* Use error_chain for ImportError and BlockImportError
* Fix error pattern matches for error_chain in miner
* Implement explicit From for AccountsError
* Fix pattern matches for ErrorKinds
* Handle ethcore error_chain in light client
* Explicitly define Result type to avoid shadowing
* Fix remaining Error pattern matches
* Fix tab space formatting
* Helps if the tests compile
* Fix error chain matching after merge