[2.2] Made blockcaps a per-channel setting.

This changes the `m_blockcaps` from a config-defined, network-wide setting to a per-channel setting defined with mode parameters.

The new syntax is `+B percent-to-match:minimum-length`
Example: `+B 50:10` will block anything over 10 characters that contains 50% or more caps.

The current `m_blockcaps` module was moved to `m_blockcaps_compat` so networks that still have 2.0 servers linked may use that.

Requested in: #463