Fix for sequence number check, messages aren't inserted in order.
Hence, we can only check after inserting all messages.
Only FullSyncDistribution has a enabled_sequence_number
Need to store max_sequence per member
Fixup
Merge pull request #253 from NielsZeilemaker/fix_sequence_number_check

Fix for sequence number check, messages aren't inserted in order.
refactory prv/pub-key checks
Add asserts for sequence numbers
Merge pull request #254 from LipuFei/fix-pkey-checks

refactory prv/pub-key checks
MAX(sequence) can be None
Merge pull request #255 from NielsZeilemaker/fix_sequence_number_check

Add asserts for sequence numbers
No more PEM in crypto interface
Fix for purge_batch_cache, and _check_full_sync
Renamed seq to last_seq
Merge pull request #256 from NielsZeilemaker/fix_sequence_number_check

Fix sequence number check
Needs to be an elif
Merge pull request #257 from NielsZeilemaker/fix_sequence_number_check

Needs to be an elif
Added load_message_by_packetid
Removed some DelayPackets as they weren't used
Merge pull request #258 from NielsZeilemaker/fix_sequence_number_check

DelayPacket rewrite