Optimize SQL query composition
Convert a unit test to manual
base_uint cleanups:
* Remove unused and broken reverse iterators
* Use charUnHex to reduce code duplication
Tidy up some source filenames:
* Add .unity suffix to mark unity sources
* Fix some relative include paths
Beast SCons tools:
* Add VSProject SCons Builder
* Add Protoc SCons Builder
* Add Beast build utilities python module
Improved SConstruct:
* Automatic source list built via directory iteration
* Build multiple toolchains and flavors simulaneously:
    - Toolchains: gcc, clang, msvc
    - Flavors: debug, release
* Documentation on aliases (top of the SConstruct file)
Fix rocksdb relative include
Tidy up includes
Add ci_char_traits
New http::client_session for making requests:
- Add 10,000 popular URL data set for unit tests
Fix clang/travis, prefer static libs when BOOST_ROOT is set.
Autobridging:

Complete implementation of bridged offers crossings. While processing an offer
A:B we consider both the A:B order book and the combined A:XRP and XRP:B books
and pick the better offers. The net result is better liquidity and potentially
better rates.

* Rearchitect core::Taker to perform direct and bridged crossings.
* Compute bridged qualities.
* Implement a new Bridged OfferCreate transactor.
* Factor out common code from the Bridged and Direct OfferCreate transactors.
* Perform flow calculations without losing accuracy.
* Rename all transactors.
* Cleanups.
[FOLD] Address issues that cropped up during review and testing:
* Ensure that partially consumed offers are placed at the right quality.
* Move functions out of headers and improve comments.
[FOLD] Fixups