Build a theme generator/picker that simplifies the process

#### Bug, feature request, or proposal:
Feature Request

#### What is the current behavior?
Custom theming angular material is cumbersome.

#### What is the use-case or motivation for changing an existing behavior?
Make it easier to modify theme based on more traditional number color palettes. Designers will often provide 3-6 colors that should encompass most of the application/website, while the material pallets have over a dozen color hues per palette, for a total of well over 50 colors that the app can use. This isn't practical to maintain unless one REALLY cares about each shade. I understand the Ng Material team is just using the official Material colors but in my opinion there is a balance to be struck.

Maybe I'm missing something from the docs but I really would prefer not to do:
$candy-app-primary: mat-palette($mat-indigo); // this palette has over dozen colors to maintain

and instead do
$candy-app-primary: mat-palette(#999); // where 999 is my primary color

And have the material theme generate the variants in some way OR do it like Bootstrap and use scss lightens/darkens mixins where appropriate.

Suggestion:
Incorporate a palette generator of some kind, perhaps using similar logic as used by the material tool.
https://material.io/design/color/the-color-system.html#tools-for-picking-colors

Review the current Angular Material theming documentation and the mat-palette usage described in the issue, then compare the proposed workflow with the linked Material color-system tool. Define how a picker or generator would accept a small set of colors and produce usable theme variants; the work is done when that workflow is specified and supported with appropriate documentation.

Written by the indexing model from the issue text.