Add possibility to create new exercise

[smartsammler]

It would be great if one could add further exercises by oneself.
Probably it is too difficult to have/take photos, but it would be cool if one could at least provide a new exercise name and short description. Then one could take notes if one of the coaches has got a new cool exercise that one wants to remember. Afterwards one could also include this new exercise into a new exercise set.

Thanks for the app.