Canvas UI Component Update - Tables

Fixes: CNVS-15536

This change removes the existing table examples from
the styleguide, but keeps the styles so as not to
break anything. New table styles and examples have been
added to the styleguide, per mockups from the UI team.

Test plan:
- Open the /styleguide page from the main Canvas url
- Click on Tables on the left-side nav
- Go through each table example and make sure it's
  working as the text says it should be (i.e., is the
  row-hover table actually showing a hover effect, etc.)
- Check the colors against color contrast requirements
  for both regular and high-contrast UIs
- NOTE: the new table styles are only being used in the
  styleguide right now, so no testing of any app areas
  is needed.

Change-Id: Iaf04703dc1e2d6a6815070fe1a4c299ab152378f
Reviewed-on: https://gerrit.instructure.com/43515
Reviewed-by: Colleen Palmer <colleen@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Anna Koalenz <akoalenz@instructure.com>
QA-Review: Matt Fairbourn <mfairbourn@instructure.com>
Product-Review: Chris Hart <chart@instructure.com>