Reachitecture filters to use insert_chat_line

Fixes #44 #46

In an effort to simplify the codebase, I changed the
filtering to occur before the chat lines are inserted
instead of by modifying their HTML. Overall, there was
a reduction of 200 LOC, including the trickiest parts
of the code.

Major behaviour changes:

* All filtering and rewriting now applies to the message
  as it was typed by the user in the chat box. The
  "@ message" rewriter was the only one that needed to
  interact with the HTML so it was removed.

* New messages that trigger an active filter are never
  added to the chat queue. Thise messages are lost
  forever, even if the filter is turned off in the future.

* Old messages already on the chat list that trigger
  a recently-activated filter will have their visibility
  toggled on and off as in the old version.

* Old messages that trigger a newly activated rewriter
  are not changed (The new rewriters cant interact with the
  HTML now)

Minor changes:

* Got rid of some duplicate functionality (allcaps and misty spam)

* Rewriters dont come with custom CSS anymore; Now the rewriter
  UI can be handled by the same code that does the filtering UI