Simplify and add features to File Browser / Project Panel

There're two different panels with similar functionality: File Browser / Project Panel. Unfortunately none of them provides features like moving files so you have to switch to Windows Explorer / MacOS Finder to do it.

As a suggestion to improve User Experience:

• Could File Browser and Project Panel not be merged into one: Project Panel
• Copy/paste files, move files, create folders should be added
• Closing a project should close all open files related to that project

For example Visual Studio Code does this in a very simple and clear way.