Convert error types

[Innectic]

Currently we just use Strings for all our Result errors. This should be changed into some kind of an enum so we actually know what the crap is happening.

[Innectic]

This should probably be done now, instead of after Constellation support is finished. Then, constellation support will just be done with the correct type of result error types.

[Innectic]

I'm also thinking we should convert HandlerResult (renamed in the constellation branch) to a more generic system - maybe remove the Nothing variant, and use Option<HandlerResult>, and just have the variants of Error and Message. Maybe we could completely replace that with a result, but that might end up making it more complicated, instead of simpler.