Draft: Change license from GPL to MIT

This PR changes the license from GPL to MIT.

We have received interest from commercial organisations and research institutions who would love to contribute to Dasher and use it to further their research and development. However, they currently cannot do that under the GPL license.

We would love for Dasher to continue getting developed and maintained long into the future so we can best serve the users of Dasher, and so we can gain more users.

We would love for these organisations to be able to contribute, so we are going through the process to change the Dasher License from GPL to MIT. This means we need to collect permission for everyone who contributed to Dasher and ask if they would be willing to make their contributions available under the MIT license.

To change the license we need permission from every contributor, if you are a contributor, please fill in this form to give us permission to relicense: https://forms.gle/RJhZWA59HWAd8n5p6

This license change is not meant to weaken the openness of Dasher, Dasher will always remain free and open source. We are looking to increase adoption and possible use cases.

If you have any other concerns or questions, please reach out to me at ghenderson@acecentre.org.uk