This adds a manual test for the QTextTable border logic.

Two HTML files are bundled as resources:

table-border-test.html: Contains various test cases for the border
logic.

table-border-test-header.html: Contains a test case for printing a table
with a repeated header.

The test application allows:
- editing
- previewing
- printing
- opening the HTML in the system browser (via temp. file)

It is possible to edit the HTML with "live preview" so new test cases
can easily be implemented.

Change-Id: Ic88488bc8b7dd74d5c03c3363f55840423462325
Reviewed-by: Shawn Rutledge <shawn.rutledge@qt.io>