Add cleaning functions

[pnxenopoulos]

Since the update to parse all demos, then handle cleaning locally, we need to build cleaning functions. These can be a few things to consider:

• warmup rounds
• knife rounds
• too short or too long rounds
• rounds with non-standard end reasons
• rounds with no score changes
• rounds outside of the bounds of the major events
• none or empty frames

These functions should likely be built into the DemoParser class.

[pnxenopoulos]

Added in 605373772efcdb9675e29c9a977000eb8e6883ba