[WIP] Move mapper logic into rom-mapper

[GustavoCaso]

#349
@solnic
As we talked about this an early WIP for extracting the logic of Mappers to rom-mapper and register via plugin, rom-rb/rom-mapper#42.

I haven't actually tested myself but I wanted to have a place where we could discuss further actions.

Following how the plugin system work I hope I have it understand it, I remove all the code related to Mappers to is PluginConfiguration.

This is PR in rom-mapper adding the behavior for register mapper

[solnic]

So, the PR on rom-mapper side looks good, so last thing to do is to update things here so the build can pass :)