Gopass store management

[jonas-pietzsch]

This adds functionality on top of managing only mounts. In addition one shall be able to init stores and clone existing stores from Git repositories.

Cloning and initialising

The other part related to this would be cloning existing (from Git repository) and initialising new password stores from the UI. Features to add to the UI:

1. Initialise a new store (gopass init <gpg-key-reference> --path <path> --store <name>)
2. Clone an existing store from Git with a name (e.g. gopass clone [email protected]/pass-work.git work) to init the store in a non-default directory (e.g. $HOME/.password-store-work)