synchronizer allows to reprocess forkids if are the same as stored on DB

[joanestebanr]

Rationale

The forkids are not linked with blocks, so when you remove blocks from Database you keep forkids information.
The synchronizer support to receive again the last forkid, but not older ones.

Implementation

If a forkid is already on database:

• if match perfectly to one in state is skipped
• If equal but differ in BlockNumber, the blockNumber is updated on database
• If differs FromBatchNumber is rejected