This introduces a much more consistent set of events within the editor
for whenever a element is added, removed or modified.
The events emited on the `RED.events` event system. The event names
take the form: `"<thing>:<action>"`.
`<thing>` can be one of:
- nodes
- flows
- subflows
- groups
- links
`<action>` can be one of:
- add
- remove
- change
The payload of the events is the object in question.
There is also:
- flows:reorder - when tabs are reordered. Payload is array of flow ids.
- workspace:clear - when the workspace is emptied - part of switching projects
The `nodes:change` event was already used by RED.nodes.dirty() to cause
the Deploy button to become active. This renames that event to:
- workspace:dirty - Payload is boolean flag for the dirty state
This commit also updates the Palette to use the subflows:change event to
only redraw subflows that have actually changed rather than refresh them
all whenever one of them *might* have changed. This removes a noticable
flicker of the icon which was needlessly being redrawn.
When listing icons provided by a module, if there is a png and svg
with the same name, only the svg will be listed.
If a node asks for a png icon which is not known, but there is a
corresponding svg, that will be used instead.
Any editor for the markdown mode will now automatically get
the markdown toolbar added.
The comment node has been updated to handle this properly and
to not add two copies of its content to the sidebar.
