* NetDB: Prep for leasesets with different expire times

   - Add new I2CP RequestVariableLeaseSetMessage
   - Send RVLSM if client supports it; handle on client side;
     disabled by default for the moment.
   - Add LeaseSet.getLatestLeaseDate()
   - Check latest, not earliest, date too far in future in KNDF.validate()
   - Check latest date too far in past in KNDF.validate()
   - Only check gateway and tunnel ID for equality in OCMOSJ lease caching to reduce churn
   - Split up KNDF.validate(RI) for efficiency, don't need to check
     signature, netid, etc. before lookups, only on store
   - Remove enforeNetID config
   - Fix major bug causing newer leasesets to be treated as older, and not stored or published
   - Increase max adjustment time of earliest lease
   - TransientDataStore cleanups
   - RouterInfo and LeaseSet equals() speedups