0.8.8update
fix releasenotes
extra files
add checkpoints.cpp in unit tests
enable checkpointed block verification
temporary fix for block reward dos
maximum block size 130% of median
Merge remote-tracking branch 'origin/master' into 0.8.8update

Latest PR merged into experimental branch.
dynamic tx size scaling for tx mempool
fix typing mismatch
typo in tx_pool.cpp
Merge branch '0.8.8update'

Update to newest version 0.8.8. See change log for details.