More ImPACT code cleanup

[gschwefer]

Hi everyone,

I finally got around to clean up the ImPACT code a bit more.

This PR has 3 major changes:

• The paths to the input templates are now TelescopeParameters. I also changed the required structure of the templates, they now need to contain a new key tel_type which contains the telescope description as a string to check if they are valid for the telescope they are being used for. This will require a little fix to all currently existing templates, but it is an easy and quick one.
• The pedestal and spe width parameters are now also TelescopeParameters. For the pedestal_width, I also included the option to read them from the monitoring. In case no values are specified, they fall back to a hardcoded value in a global dict.
• Finally, for the tests, I removed the need for the dummy_reconstructor option/variable

I look forward to your comments and to discussion on the implementation of these things.