Implement Rename Request

[AnHeuermann]

Description

Implement Rename Request.

This needs information about what declarations are available, where is this declaration used (over multiple files) and so on.

Desired Features

• [ ] Rename stuff
  • Rename variables inside classes
  • Rename classes (models, packages) and update includes / usages in all other files / packages / classes / ...
• [ ] Server tests
• [ ] Client end to end tests