[x] Improve color definition for log texts, taking into account the current theme (palette) and adjusting some colors to work well on both environments light and dark.
[x] DB panels' input widgets:
[x] Background color according to validator state.
[x] Topping wizard's structure preview now visible in night mode.
Requires https://github.com/opengisch/QgisModelBakerLibrary/pull/101
Screenshots of new look and feel (default theme added for reference):
Fix #568