Make parser a separate component

[piotrm50]

Parser needs to be a separate component from the Tangle.
Other components need to be able to attach their own filters to the parser. For example:

• TSC check - drop any message that doesn’t satisfy TSC.
• Drop blocks that have different epoch commitments and notify notarization manager.

When a new block is succesfully parsed, it needs to be attached to the Tangle component.