Add ledger.history.mismatch insight statistic
Make sure we update mTNByID when we replace the root
Improve parallelization of getRippleLines
Better function arguments (RIPD-590).
Protect people from ledger-spew (RIPD-514) and remove cruft.

* Now --display=ledger gives a pruned full ledger when --full is true.

* If you really want the 120MB full ledger, use
  --display='ledger(true)'

* Removed duplicate code, added Log.warn, added some warnings (part of RIPD-509)
Better errors, cache command. (RIPD-509, RIPD-525)
Better ledger summaries (RIPD-527).

* Also, one new error message in the error table!
Better summaries. (RIPD-527) Clear cache. (RIPD-530)
Process cached ledgers not on the server. (RIPD-531)
Offline mode. (RIPD-529)  Fix ledger names. (RIPD-511)