Persistence sp support

Persistence + SP work.

Active crowdsales are now persisted (with the database of token issuance's)
immutable SP info is stored in a level DB
* there is a side index that allows looking up SPID based on TXID

Next-available SPIDs are considered global state and backed up as part of persistence.  This means that if the persistence files become corrupt and have to rewind to find good files that any re-parsed SP's will get their same SPIDs.  It also means that in the case that persisted state is used to handle re-orgs, that spids will be consistent.

!!BIG NOTE!! This is build on top of faizkhan00:add-maths @dfef432, so pulling this implicitly pulls that.