[neo-project/neo] Staked free tx [idea] (#357)

We can implement filters in two ways: (1) directly on consensus nodes, they vote to block stakes according to specific rules (2) on relay nodes, that will simply block relay transactions they believe are misbehavior (3) relay nodes can pass messages to the pool and add extra information to help consensus judge the misbehavior (they could indicate why they believe punishment is necessary, for example, listing a group of bad transactions and even circular analysis that can be done better with heavy offline processing)