Improve transaction fee and execution logic (RIPD-323):
* tecINSUFF_FEE if balance doesn't cover fee
* Ensure transaction recovery is deterministic
* Reduce transaction retries
Remove SHAMapNodeID from SHAMapTreeNode (RIPD-347)
This resolves the "right data, wrong ID" issue in the
tree node cache.
Freeze flags: (RIPD-394)
 * Define all flags
 * Set/clear bits in transactors
 * Frozen line counts towards reserve, is non-default
 * Report trust line state
Update freeze tests
* Conditionally skip freeze enforcement tests
* Honour remote.fee_cushion setting
* Workaround ripple-lib regression
* Don't use mocha features from wrong version
Fix book_offers limit parameter (RIPD-295)

Conflicts:
	src/ripple/module/app/misc/NetworkOPs.cpp
Fix bugs, typo in SHAMapNodeID
Set version to 0.26.0
HTTP support improvements:
* Case insensitive equality, inequality operators for strings
* Improvements to message_parser
* Tidy up HTTP method enumeration
* boost::asio buffer helpers
Structured Overlay work:
* New I/O paths for client and server role
* New handshake_analyzer detects the peer protocol
* New basic_message class for parsing and storing HTTP messages
* Conditional compilation for selective feature enabling.
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