Include UnitProxyProvider into Controller

All of inclusion dependencies are defined in railtie
Pass :unit option to active if option in invoking

Useful when we'd like to judge condition by invoked unit
Fix nil error when unit is not found and error is disabled
Add alias from callback to function for backward compatibility
Add css classes for backward compatibility

Move the responsibility to create css classes into Function.
We might want to change this classes via configurations
Add a run_default feature to invoke default behavior from function.

Also, run_default is invoked in rescue section.
v0.0.5