New types Account, Currency, Directory:
* New tagged uint types.
* Extract to_string functions from header to hide dependencies.
* Include what you use and C++11 for cleanups.
Move static treeNodeCache from SHAMap to the Application

These changes address two JIRA issues:

 - 291 unittest reported leaked objects
 - 292 SHAMap::treeNodeCache should be a dependency injection

The treeNodeCache was a static member of SHAMap.  It's now a
non-static member of the Application accessed through
getTreeNodeCache().  That addressed JIRA 291

The SHAMap constructors were adjusted so the treeNodeCache is
passed in to the constructor.  That addresses JIRA 292,  It required
that any code constructing a SHAMap needed to be edited to pass
the new parameter to the constructed SHAMap.

In the mean time, SHAMap was examined for dead/unused code and
interfaces that could be made private.  Dead and unused interfaces
were removed and methods that could be private were made private.
Fix bug in VSProject when no LIBPATH in env
Add ASIO strand to StatsDCollector
Autobridging:
* Remove legacy OfferCreate transactor
* Misc. cleanups on LedgerEntrySet
* Fix a subtle bug with arithmetic operations on Quality
* Sanity check offers after taking
New types Account, Currency, Directory:
* New tagged uint types.
* Extract to_string functions from header to hide dependencies.
* Include what you use and C++11 for cleanups.
Update state during pathfinding
During playback close ledger before accepting
Restore checkpointed ledger under all paths in PathFind.
Tighten up some serialization checks
Improvements to HTTP parsing
Structured Overlay support:
* Add Peer Protocol detector
* Add RIPPLE_SINGLE_IO_SERVICE_THREAD setting
* Preliminary HTTP header parsing logic (disabled)
Update ripple-lib integration tests
New integration tests:
* New tests for autobridging and freeze
* Discrepancy detection tests
* Don't let Mocha suppress load time errors
In JSON, output unprintable currency codes as hex
Fix a case where we put an extra node in the SHAMapDiff
Add new memo restrictions
Add README.md for ledger process
Update Sconstruct
Cleanup confusion of ledger base versus ledger header

The "ledger header" is the chunk of data that hashes to the
ledger's hash. It contains the sequence number, parent hash,
hash of the previous ledger, hash of the root node of the
state tree, and so on.

The term "ledger base" refers to a particular type of query
and response used in the ledger fetch process that includes
the ledger header but may also contain other information
such as the root node of the state tree.