refactor(all components): use yandex BEM css code style

[Kimi-Gao]

• Make sure that you propose PR to right branch: bugfix for master, feature for latest active branch feature-x.x.
• Make sure that you follow earth-ui's code convention.
• Rebase before creating a PR to keep commit history clear.
• Add some descriptions and refer relative issues for you PR.

Description

• Use yandex BEM css code style to rename all less/jsx class.
• The structure of the BEM follows the pattern:
  • block-name_modifier-name
  • block-name__element-name_modifier-name
• Use prefixCls and prefix-cls variables to replace earthui in js/less

[weiyuxuan]

👍

[weiyuxuan]

You could declare a variable for UI name:

@ui-prefix: earthui;

And use it in every component stylesheet like this:

@avatar-prefix: ~"@{ui-prefix}-avatar";

.@avatar-prefix {
  vertical-align: top;
}