Move Official Input Web Components to Combined Repo

Web components that were moved from their individual repos, renamed and adjusted slightly to be styled more consistently:

• d2l-input-checkbox (previously d2l-checkbox)
• d2l-input-search (previously d2l-search)
• d2l-input-text (previously d2l-text-input)
• d2l-input-textarea (previously d2l-textarea)

Initial release

Merge pull request #32 from BrightspaceUI/fix-color-warning

fixes #31: no need to include colors as they're global