add thread pooling
make the thread pool a bit smarter and clean up the code
Make ThreadPool autoloadable
Update the thread pool to accept a block and choose more semantic names
Remove extra methods and use Config.workers
Add a custom logger level for "internal omnibus" messages

Prior to this commit, there was a conflation between an Omnibus debug
message and a build debug message. This commit adds a new log level
called "internal" that is more verbose than debug.
Add "nothing" log level for seriously nothing
Do not use a lazy_default for the log level