Minor GUI issues

[borysiasty]

1. There is hardcoded white background, what causes "white on white" in dark schemes. (fixed in #23)

2. The dialog may take a second or two to open, so switching to the wait cursor would make a nice impression.

   After some thinking: as it's not so important, maybe better to wait a bit and ensure it works stable. A Python exception during scanning the dependencies would leave user with the wait cursor forever.

3. If there is no installed packages yet, the Show library folder in explorer action does nothing. Very minor issue, but maybe pushing kind of "nothing to do yet" message would be nice.

[m-kuhn]

@borysiasty fixed by #23 ?

[borysiasty]

@m-kuhn Yep

[borysiasty]

(I mean the first point only)

[m-kuhn]

2. The dialog may take a second or two to open, so switching to the wait cursor would make a nice impression.
   After some thinking: as it's not so important, maybe better to wait a bit and ensure it works stable. A Python exception during scanning the dependencies would leave user with the wait cursor forever.

We could use qgis/QGIS#4944

3. If there is no installed packages yet, the Show library folder in explorer action does nothing. Very minor issue, but maybe pushing kind of "nothing to do yet" message would be nice.

👍