Feat/dark themes

[m0ksem]

Better themes support and dark themes as well.

Breaking changes.

• Colors changed according to Create color themes as service #744 (comment) (removed white, dark, black and gray colors)
  Added new colors to color-config: textLight, textDark, background, backgroundSoft, backgroundMute, shadow, focus.
• Added auto text color for VaTimePicker and VaDatePicker relative to their backgrounds. Here can be performance issues, but it is optimized by maximum.
• Removed useless CSS variables
• Some component colors maybe changed to fit new color pallet.

TODO

• Better types for vuestic color config colors (we must require colors such as primary, background etc, but user must be able to add own.)
• Check if all colors used correctly.

closes #744
closes #1590
closes #1255
closes #1385
closes #757
closes #1858
closes #1867

[m0ksem]

Theme demk from docs for now.

[m0ksem]

[m0ksem]

Merging to prevent conflicts in feture PRs. Stuff to do:

• Optimize useElementBackgorund (with caching)
• Update colors demo.
• Setup theme service config.
• Maybe rename color names.