split modules to separate repos to improve modularity

[achubaty]

1. easier to not use certain modules (like we did for AB NRV, where we provided our our regime pars);
2. finer-grain control over module updates (currently unable to pull updates for specific modules; all-or-none), which reduces merge conflicts introduced when scfm being used in multiple projects.

@SteveCumming I understand that we had previously discussed this and agreed to hold off because you were actively developing and encountered issues using git submodules, but now that scfm is primarily being maintained by Ian (with support from me), this will vastly simplify scfm integration across multiple projects. Additionally, Eliot's recent creation of SpaDES.install::getModule() allows users to get modules without needing to use git.

@ianmseddy this is high on my TODO list and I'd like to discuss further, as it will have implications for existing/ongoing projects using scfm.

[achubaty]

this is still on my radar, to be completed after new package sfcmutils used throughout modules.