Description

We only want to pass solid transactions to other nodes.

Motivation

Non solid transactions can't affect the ledger state. They might be plane spam.
No need to gossip them.

Requirements

1. If a transaction gets quickly solid upon receival, add it to the networking broadcast queue
2. Once a transaction becomes solid via the TransactionValidator solidifier, add it to the broadcast queue.
3. Once a transaction becomes solid via the MilestoneSolidifier add it to the broadcast queue
4. Once a transaction becomes solid via TipsSolidifier (off by default) add it to the broadcast queue.