Relates to #9948.
Having the project upgrade messages in the Messages panel means that
users can refer to them as they clean up their projects to bring them
into the v17 format.
Relates to #9948. Starts basic support for v2.0 projects.
For all operating modes:
- Remove blank projects / untitled projects mode
- Add Open Project Folder buttons and links
- Remove Project Save As
- Render uses in-memory XML
- Upgrade to v2.0 project file (along with checks)
For v2.0 projects:
- Remove 'Add File to Project'
- Populate Files to list all files in folder (note: consider efficiency
here as currently files are parsed for subfile data)
- Version 2.0 project options and defaults
