Show BW projects filesystem directory to user

[tmillross]

The AB user may like to know where their data project and database is being stored by Brightway on disk. For example, to copy to another computer, configure version control, or just to explore. Brightway has a number of possible data storage options. Alternative data storage approaches cannot yet be managed in AB, but the user may have made some BW edits at the command line. The filepath is different for each OS. For Windows, the default is non-obvious, particularly the "pylca":

C:\Users[username]\AppData\Local\pylca\Brightway3

Therefore I believe users may benefit from a simple interface element which either displays or opens their projects filepath.

There are a number of candidate locations (open to suggestions) for including this functionality, which you'd probably expect to find in the projects and databases section of the interface. For now I'm thinking of a simple "show filepath" button->label to the right of "Delete current". Pending a future reorganisation of this section.