Refactor string-to-integer conversions
Cleanups:
* Remove obsolete config variables
* Reduce coupling
* Use C++11 ownership containers
* Use auto when it makes sense
* Detect edge-case in unit tests
* Reduce the number of LedgerEntrySet public members
Add ledger cleaner documentation (RIPD-555)
Fix handling of HTTP/S keep-alives (RIPD-556)
[FOLD] fix asio socket handling
[FOLD] Remove unused data member
[FOLD] Add session id and request count histogram
[FOLD] Change print name to 'http'
[FOLD] ssl shutdown fixes
[FOLD] refine log severities