Add color scheme modes and color scheme custom generator support

[AIIX]

• Adds dark, light color scheme theme mode selection and preview support
• Adds generate custom color schemes settings page, delegates, views and settings bus handler
• Adds button sounds to all settings menus

[codecov]

Codecov Report

Merging #140 (74b2b75) into dev (6ceb058) will increase coverage by 2.46%.
The diff coverage is 41.93%.

@@            Coverage Diff             @@
##              dev     #140      +/-   ##
==========================================
+ Coverage   50.35%   52.82%   +2.46%     
==========================================
  Files         119      150      +31     
  Lines       10077     9674     -403     
==========================================
+ Hits         5074     5110      +36     
+ Misses       5003     4564     -439     

Impacted Files	Coverage Δ
mycroft/audio/__main__.py	0.00% <0.00%> (ø)
mycroft/client/enclosure/__main__.py	0.00% <0.00%> (ø)
mycroft/client/enclosure/mark1/arduino.py	0.00% <0.00%> (ø)
mycroft/client/enclosure/mark1/eyes.py	0.00% <0.00%> (ø)
mycroft/client/enclosure/mark1/mouth.py	0.00% <0.00%> (ø)
mycroft/client/speech/__main__.py	0.00% <0.00%> (ø)
mycroft/client/speech/hotword_factory.py	0.00% <0.00%> (-88.89%)	⬇️
mycroft/client/speech/service.py	0.00% <0.00%> (ø)
mycroft/client/speech/silence.py	0.00% <0.00%> (-42.86%)	⬇️
mycroft/client/text/__init__.py	0.00% <0.00%> (ø)
... and 117 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 5287dc5...74b2b75. Read the comment docs.