1.2.1

Paperwork-GUI 1.2.1:

• Add source code of Windows installer (NSIS installer) generator
• Scanner support / Multi-scan: Cancel also successful scan session. Otherwise
  some scanner won't allow new scan sessions later.
• Remove gi version warnings when starting (thanks to Matthieu Coudron)
• Documentation: Add missing stdeb dependencies (thanks to Notkea)
• paperwork-shell: Fix command 'scan'
• paperwork-shell install: add docstring
• Fix dialog 'about'

Paperwork-backend 1.2.1:

• paperwork-shell: improve help string of 'paperwork-shell chkdeps'
• Fix label deletion / renaming
• Windows: Fix FS.safe() when used for PDF import
• Windows: Fix FS.unsafe() (used for PDF export)