Update information on mesh2hrtf.org

[f-brinkmann]

I checked mesh2hrtf.org and would suggest the following

• [ ] Add a reference of our paper when published in the About Mesh2HRTF section
• [x] Update the license information
• [x] Update the articles that should be cited when using Mesh2HRTF
• [x] Update list of publications that used Mesh2HRTF (we could also list third party publications, if we wanted to: https://scholar.google.com/scholar?start=0&hl=de&as_sdt=2005&sciodt=0,5&cites=2498946778044165472&scipsc=)
• [x] In the Support section, delete the Help me! part.

[f-brinkmann]

noved to #25