feat(theming): use internal theme functions instead of materials. (closes #446) (closes #450) (closes #232) (closes #423)

[emoralesb05]

Description

#446
#450
#232
#423

Since we were leveraging @angular/material themes, we were using the scss files in their module, but this cause issues when using relative paths to node_modules or ~ (since ~ makes it tightly coupled to sass-loader/webpack)

Its better to just have the files internally and use those to avoid using ~.

What's included?

• chore(scss): upgrade all internal sass style files to latest.
• chore(): remove hardcoded background for md-list-avatar
• chore(): remove hardcoded .mat-list-text p color
• chore(): replace md-color by mat-color
• fix(): remove ~ from highlight and markdown
• fix(theming): use internal theme functions instead of materials
• fix(validation): move hardcoded invalid input theme into common-theme

Test Steps

• ng serve
• See that all styles work fine

General Tests for Every PR

• ng serve --aot still works.
• npm run lint passes.
• npm test passes and code coverage is not lower.
• npm run build still works.

Screenshots or link to CodePen/Plunker/JSfiddle