[MAIN] Libzerocoin patch

[presstab]

• This patches up the recent exploit that was found in 3rd party library libzerocoin. The exploit allowed for multiple serial #'s to be created from a single minted zerocoin and still be considered valid.

• Accumulators are triggered to be recalculated to exclude any mints that stem from invalid spends. This recalculation will occur on block 908000. Accumulator checkpoints that were added while invalid spends/mints were made will be deleted from the database automatically.

• The money supply (both PIV and zPIV) will be reindexed automatically on block 908001.

• -reindexmoneysupply startup flag has been added which will recalculated the money supply on startup.

• getinfo and getblock RPC now print the zPIV supply for each zPIV denomination.

• Checkpoints are added in spots where the network saw disagreement and lack of consensus.

• An additional, and redundant, check is added that ensures zerocoinmint transactions are seen as unspendable by CCoins. (unrelated to exploit, but an additional safety check).

• This specific pull request has zPIV transactions hard coded to be disabled. It is important to note that [Main] Allow for zPIV maintenance mode #388 should be applied after this PR to have proper functionality.

• Any stolen funds that were not reaccumulated as zPIV will be locked, with the exception of funds that were filtered through Bittrex.

• Protocol is bumped to 70912

• Spork_11 is added.