Leginon

This refactoring is done with an eye to eventually allow reusability of connections.

connections always instantiate mysql class which clobbers the connection state within. given the existing caller interface the eventual solution should manage connections at the class (static) level.

1. remove previous invalid attempts to renew/reuse connections which just added noise to the logs
2. ability to generate backtraces for debugging (off by default)
3. new internal variable to keep connection state