Fixes #1442
Fixes #2375
Progress on #2358

This is part 1 because I have cleaned up the __Table components, but not the __TableRow components.

Code cleanup:

• Create a TableBase component to handle common logic of tables:
  • Show <Loader/> when loading.
  • Show "no results" message when empty.
  • Render column headers with the name of each column.
  • Highlight the active column with underline and triangle up/down icon.
  • Sort the items in the table when clicking on the column header.
• Write tests for this core logic of the TableBase and TableHeaderCell.
• Use the TableBase in existing components:
  • AssetList - converted to function component
  • CollectionList - converted to function component
  • SketchList - converted to function component
  • Collection - still a class component because I have other open PRs that touch this (Move CollectionMetadata into its own component. #2253)
• Sorting is handled internally by the TableBase, so remove sorting from Redux.
  • Delete the sorting reducer, actions, and selectors.
  • Rework one test of SketchList which checked redux actions.
• Use class sketches-table on all tables (can add additional classes alongside it), and delete SCSS properties on asset-table which are duplicates.
• Migrate to styled-components:
  • All table header styles.
  • Empty message style.

Bug Fixes:

• Sketches table in Collection component can be sorted (Sketches table on collection page is not sortable #2375)
• SketchList column header "Sketch" now shows the correct aria-label. It was "Sort by Sketch descending." but should be "ascending".

New Features:

• AssetList can be sorted.
• Added ARIA attributes aria-sort and aria-pressed to column headers.

I have verified that this pull request:

• has no linting errors (npm run lint)
• has no test errors (npm run test)
• is from a uniquely-named feature branch and is up to date with the develop branch.
• is descriptively named and links to an issue number, i.e. Fixes #123