allow knowls to be used to display hints and solutions

Add ability to show hints and solutions as knowls.

This involved defining some configuration flags in defaults.config. Read the comments there for configuration details or read the comments in commit 751c002...

There are minor tweaks to math3 theme to control the floating boxes. (math2 is not as current -- you can use it for comparision)

I changed the default.config file so that it reads the database.conf.dist file by default. This means that you no longer have to change database.conf when upgrading. If you must modify database.conf.dist you can uncomment the "include(database.conf)" line at the end of database.conf.dist.