Respect table attributes in Antora output

As part of the overall docs UI changes, make sure that our document output respects the AsciiDoc table frame and grid attributes.

• If you don’t specify frame or grid attributes, asciidoctor.js adds the classes frame-all grid-all to the output table element by default. If you specify frame=none,grid=none in the attribute list for a table, asciidoctor.js adds the classes frame-none grid-none to the output table element instead.

• In the default asciidoctor.js stylesheet, tables have 0-width borders by default. The default asciidoctor.js stylesheet selects the frame-all grid-all classes, and adds borders with width 1. Tables with the classes frame-none grid-none fall back by default on 0-width borders.

• In our stylesheet, tables have borders of width 1 by default (note). Our stylesheet ignores the frame-none or grid-none classes. In fact it ignores any frame-* or grid-* classes. So specifying any frame or grid attributes for a table has no effect.

• To fix this, we need to add style rules to the stylesheet to select all the possible table-* and grid-* classes. The place to change this is src/css/doc.css in the docs-ui project.

note In fact, our stylesheet has self-contradictory rules for table borders, but the rule specifying borders of width 1 takes precedence.