Implement BeginBlock and EndBlock event filtering mechanisms

[pharr117]

We need a way to filter BeginBlock and EndBlock events based on some key conditions.

Some options for filtering may look like:

1. Filtering event by Type field
2. Filtering event by Type + Attribute key/value
3. Filtering by a sequential group of Type fields (e.g. only index coin_received immediately followed by a coinbase event)
4. All of the above