README.md and CHANGELOG.md should be editable

[rallek]

Idea/Feature request

Modulestudio do have already an integrated editor. Why not making README and CHANGELOG editable inside MOST? In the menu they may appear under window/views/README.md or window/views/CHANGELOG.md. They should be stored beside the mostapp file in the MostWorkspace folder. If they are available in the MostWorkspace folder of the model they should be used instead of the automatic creation. Handling for marked files or skipped files as usual.