Strip namespaces from downloadable files

Change handling of file names during download to enable security checks

Download PNG via AJAX

When creating a diagram, check for existing files

move CSP definition to central file

We want to be sure we define (and potentially change) this only once

CSP: Allow google fonts in diagrams

make PNG cache optional

save PNG file with the SVG for use in PDF export

Move handler for the move plugin into the appropriate action class

Add support for move plugin

Fixes #32

fix editing embedded diagrams

ensure only diagram files can be edited/selected

prosemirror: fix embedded saving

The node type wasn't saved back correctly from the form.

proper differentiation between mediafile and embed in prosemirror

initial work on making embedded diagrams work in prosemirror

Simple Prosemirror menu button and edit form

Rudimentary prosemirror support (as yet only view)

refactored action components

more strict separation of modes

more refactoring for mediafile diagrams

Editing embedded diagrams now works

more checks on the embedded SVG

we only want to work with diagrams.net created SVGs

first round trip editing for mediafiles works with new class

add configuration option to enable/disable embed mode

Add ajax backends for loading/saving embedded SVGs

This also renames the syntax classes to be easier to distinguish