* Light client on-demand request for headers range.
* Cache headers in HeaderWithAncestors response.
Also fulfills request locally if all headers are in cache.
* LightFetch::logs fetches missing headers on demand.
* LightFetch::logs limit the number of headers requested at a time.
* LightFetch::logs refactor header fetching logic.
* Enforce limit on header range length in light client logs request.
* Fix light request tests after struct change.
* Respond to review comments.
* 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
* rpc: transaction/receipt requests made async
* rpc: light client fetches transaction and uncle by hash/index
* on_demand: request type for transaction index
* serve transaction index requests in light protocol
* add a test for transaction index serving
* fetch transaction and receipts by hash on light client
* fix decoding tests
* light: more lenient cost table parsing (backwards compatible)
* fix tests and warnings
* LES -> PIP
* Update provider.rs
* proper doc comments for public functions
* header back-references for on demand
* initial back-reference implementation for on demand requests
* answer requests from cache
* answer requests from cache, add tests
* strongly typed responses for vectors of homogeneous requests
* fix fallout in RPC without optimizing
* fixed naming of rlp modules
* RlpStream cleanup
* appending short rlp lists (0...55 bytes) is 25% faster
* RlpStream does not use bytes module, nor trait Stream
* removed unused code from rlp module
* compiling ethcore-util with new rlp serialization
* compiling parity with new rlp serialization
* fixed compiling ethcore-light with new rlp serialization
* fixed compiling ethsync with new rlp serialization
* removed redundant comment, print
* removed redundant double-space
* replace usage of WriteBytesExt with ByteOrder
