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

查看当前的 Angular Material theming 文档以及 issue 中描述的 mat-palette 用法，然后将提议的工作流与链接的 Material color-system 工具进行比较。定义 picker 或 generator 如何接受一小组颜色并生成可用的主题变体；当该工作流完成规范定义并有适当的文档支持时，工作即告完成。

由索引模型根据 Issue 内容生成。