Windows SMB share/mount refactoring
Windows SMB share/mount refactoring

- Using name variables for clarity
- Prefix docksal SMB shares with "docksal-" to avoid conflicts with existing shares
- doing umount before mount in smb_share_mount to simplify debugging (e.g. `fin debug docker_machine_mount_smb` to remount the share)

Relates to #117

docksal/docksal