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.
Remove boost::hash_value() overloads.
This addresses https://ripplelabs.atlassian.net/browse/RIPD-102
Fix base log partition severity