Pluggable naming strategies

[fredcooke]

Currently works with opinionated maven-style repo naming, a flat option would make this more globally useful. In branchout settings just have a model: or naming: field with flat, maven, etc in it. Unknown values should print acceptable values on failure.

[fredcooke]

Thinking about this more recently. I actually do a groups style layout myself for my own stuff that I'd like to use this with, however the group is not included in the repos because it doesn't make sense to. What would make sense is a .branchoutgroups file IN each repo and branchout can clone the repo to eg .branchout-tmp and then see what's there on the default branch (whatever it's called :-p) and mkdir/mv repo as needed. This would be super nice, I'd start using it immediately with just that change.

Could be driven by a top level Branchoutfile option layoutStrategy or similar eg groupByRepoName or groupByDotBranchoutgroups or similar? CC @stickycode