FIX: Add 1d Button to timespan_btns Button Group

[zdomke]

Fixing a mistake that was made when creating the quick timespan button for 1 day (labeled '1d'). The button was mistakenly left out of the timespan_btns button group, resulting in:

• the toggling not being exclusive to the other timespan buttons
• the button having no functionality when clicked/toggled

The solution was simply to add it in designer.

[zdomke]

Note: Tests for default model values and model validity will fail with the current version of PyDM (at the time of writing this) as some PyDM models will still return empty QVariants when a request is invalid. I have already made a PR for this: https://github.com/slaclab/pydm/pull/1122

Second Note: Some other test may fail due to a bug in FormulaCurveItems. I already have a PR to fix this bug as well. We can ignore tests with the same error message as the PR: https://github.com/slaclab/pydm/pull/1124