Added configuration files and various other fixes.

WhileyWeb now uses a configuration file called `config.py` to remove all the host-specific information from this repository. The repository includes an `example-config.py` which you should copy and modify to suit your needs. Comments inside the example config explain each configuration option. This fixes #5.

Other changes:

* Fixed bug where Ace editor was showing weird characters when browser using ISO-8859-1 encoding (#13).
* Added error underlining.
* Fixed CSS error for top error messages (shown with invalid program ID).
* Disabled the extremely verbose CherryPy logging in favour of a config-specified error log file.