Merge desktop and api changes

[aorin]

The dev branch contains a lot of changes compared to the main one, it contains api related changes by @MLumme and then it adds the whole desktop app. From the scripts especially the classifier has changed a lot, it now has more config parameters and it works for both keras and tflite models. All the changed have been made so that nothing breaks in the existing scripts, but it may be a good idea to test that the scripts work as before before merging this.

[mikkohei13]

@aorin @MLumme would it be better to separate the desktop app from this repository? The repo now contains code for many different things not tightly related: desktop app, API and command line tool to make identifications and analyze id results.

[aorin]

The app code is inside the app folder so it is pretty separated. However, all of these (desktop app, API and command like tool) use scripts classifier and functions. They contain quite much code and I thought it's a good idea to share them since that way the changes will be available for all of these three automatically (for example when adding the support for bat model). Ideally if these three are in a same repo they would all have separate folders (so there would be app, api, cli and shared). If they are separate, then the classifier code needs to be duplicated or shared some way (as a pip package for example) so maybe more work at this point. What would you prefer?