This is the next step on converting all internal views to custom
elements instead of using SpacePen. The TextEditorElement instances
are associated with ::__spacePenView fields that are used for supporting
legacy access paths via atom.workspaceView.
This changes all APIs concerning paths and repositories on the project
to be plural, preparing us to switch to multi-folder projects. It
doesn’t make any changes to actually support multiple folders. Instead
we just wrap the previous return values in singleton arrays.
* constructor ‘path’ params -> ‘paths’
* getRootDirectory -> getDirectories
* getPath -> getPaths
* setPath -> setPaths
* getRepo -> getRepositories