add `projectPath` and `packagePath` to `getPaths()`

[CeresBarros]

When using SpaDES.project, projectPath and packagePath get defined but not propagated into the output or a simList using it.

I think it'd be good to pass these paths to the simList, if they have been set, and make them accessible with getPaths -- even if SpaDES.core is not using them explicitly

I suggest that simInit doest not try to guess these paths if they are not passed via simInit(..., paths). In that case they are just "omited" (as they are being now)