Document branch model used for SDLC

[blipper]

Is your feature request related to a problem? Please describe. I raised a bunch of prs against master. Apparently dev is the appropriate place for this.

Describe the solution you'd like Document this

Describe alternatives you've considered A clear and concise description of any alternative solutions or features you've considered.

Additional context Add any other context or screenshots about the feature request here.

[MMory]

We could delegate this to one of our students I guess.

[fabianbs96]

See https://github.com/secure-software-engineering/phasar/wiki/Coding-Conventions#branches