Autotest ONIE

This is beginning of the testing framework for ONIE.

At the moment, it provides just the groundwork:
* Parameter validation
* Dynamic module loading
* Dynamic test definitions
* Basic documentation
```
LOADED_MODULES[module_string] = __import__(module_string)
```
If the module does not exist, it'll barf, else it'll be stored in the dict (whats the use of that dict, BTW?)