save a serialization version number in blobs so that we never resume from wrong state

[jbrzusto]

This safeguard is long-overdue.

[jbrzusto]

and is built into boost::serialization, so what took me so long?!

[jbrzusto]

Reopening because I failed to read the boost::serialization docs properly: the version parameter doesn't do anything except get passed to serialize methods of classes. It's up to the Tag_Foray::resume() to actually notice (and fail gracefully) on an incompatible version.

[jbrzusto]

Fix

We'll distinguish between minor and major serialization versions:

• serialized state is incompatible across changes to major version
• serialized state is compatible across changes to minor version, but class methods have to deal with it. The serialization version will be (major << 16) | minor
• [x] record a serialization version in new column version of the batchState table
• [x] change DB_Filer load_findtags_state / save_findtags_state: if the serialization major version has changed, fail resume() gracefully.
• [x] change motusServer::ensureRecvDBTables() to include batchState.version
• [x] apply alter table batchState add column version integer to each recv DB
• [x] delete all receiver saved state

[jbrzusto]

this is done now.