Scheduled actions - Add a slot count (or Finish time) to allow quicker set up

[dqj999]

When scheduling actions over several hours it it slow to set up.

Adding a count of the number of slots that this applies to would speed things up.

PS Scheduled actions are a nice feature that I will be using to put the inverter into Hold mode to save more battery for the expensive slots later in the day.

[Webreaper]

Seems reasonable. I was trying to keep it super simple, but I can see how this would help.

I'll do this when I tackle the changes discussed in #96