Added spam filter

Added spam filter functionality to message server and message server
monitor.
Tweaks for spam

Added non-randomized example tokens at start. Added filter limitation.
Ion storm will replace tokens with garbage. Spam disaster lasts longer
and is more severe.
Tweaks for spam #2

Added brackets surrounding tokens to make whitespace and empty tokens
removable.
Slightly modified ion storm behavior.
Increased duration required to stop spam to 5 minutes.
Added ability to expand spam filter limit with installation of message
monitor circuits.
People will see why their message been discarded.
Discarded messages will be highlighted with red color in message log.
Fix

No everlasting events.
Merge pull request #5086 from UristMcKerman/spam-filter

Spam filter