samba: web and hidden shares and other improvements

Ideas to improve the Samba app:

• edit the name of the share
• hidden share (browseable = no)
• read-only share (only admins can write). Suggested in https://salsa.debian.org/freedombox-team/plinth/issues/1758#note_149553.
• web share, over apache/http (read-only, only for Group and Home shares, users can create a public share by creating public_html subdirectory under the Home share. Related issues #1758 (closed), #1799
• DONE Hide common system partitions like /boot and /boot/firmware
• DONE Rename File Sharing to Network File Storage (https://discuss.freedombox.org/t/what-is-samba-app/699/5)
• ? allow to enable traffic encryption for the share (smb encrypt = required). All modern clients should support it, slows down file transfers.
• ? store Samba passwords (schema) in LDAP
• ? storage selection form - suggest to enable Samba
• ? samba daemon - use systemd logging