In InboundLedgers::acquire, properly return a ledger if we are
able to create one immediately.
In LedgerMaster::walkHashBySeq, don't walk the whole ledger if
we already know we have it.
This performs a deep refactor on the Ledger class and its supporting
classes, in preparation for the move to shared_ptr<SLE const> in
places where the SLE is immutable and we are currently using
shared_ptr<SLE>.
Member functions are converted to free functions, the SLECache is an
explicit parameter, one line convenience functions are removed to
streamline the interface. Some callers are changed to use <SLE const>
instead of <SLE>
SLECache:
* Moved to its own header file
RippleState:
* Remove unused functions
* Store the SLE as const
* Simplify callers
AccountState:
* Remove unused members
* Simplify existing members
Ledger:
* Replace writeBack with insert and update
* Remove unused functions
* Remove LedgerStateParams
* Move getLastFullLedger to Application
* add entryCacheI, exists, fetch, erase
* Use boost::optional where it makes sense
* Make member functions free functions
Free functions:
* fetch: cache-aware SLE retrieval
* forEachItem, forEachItemAfter
* (various)
* Inject dependencies, make functions free and levelize
* Add comments to document the intent behind the code
* Reduce class public interfaces
* Remove support for proposals without ledger hashes
