Refactored Toolwindow

Alright, here is a PR, which moves the creation of the Go-Toolwindow into its own files.

Now Intellij is responsible for creating/disposing the tool-window.
Apart from that, a lot of code for creating the tool window is removed from the ProfileStates and the Debug-Actions.

Another advantage is, that in the future we can create a more sophisticated UI
with the GoToolWindow class.