Mad-gui

**1. Labels**

- events snapped to a wrong position when added via mouse/keyboard, because sampling rate was not considered. It needs to be this way, since otherwise the positions are not correct when reloading events from a `.mad_gui` file.
- event labels can now be passed to the gui. Press and hold ctrl to add events
- region labels can be defined to include one or more event labels

**2. Bugs**
- fixed an issue with axis going off when having several monitors
- enabled using openGL and autodownsampling (see config.settings), which gives a high performance boost in loading and moving large datasets

- Relax pandas dependency to ease dependency handling for developers who build using our GUI. If developers wanted to use our ExampleAlgrotihm and ExampleImporter, they now have to use the code from github and use `poetry install` or manually take care that the correct pandas version is installed.
- Enable to load annotaions in custom format.
- Give more feedback to users and developers if things go wrong.

We updated the docs and added the possibility to create a stand-alone executable which runs on Microsoft Windows.