Add wp_common.tex.

File should have been added, but was ignored due to .gitignore file.
Add first cut of test suites.

Test suite and test registration methods have been stubbed out and
tested. Looks good so far, but there's a lot more to do, particularly
with regard to code cleanup and documentation. Definitely need to work
on detangling the source.
Reorganize source file for better comprehension.

I'm reordering the wp_test.w file in preparation for more comprehensive
documentation. I've made no other code changes.
Merge branch 'test-suites' of github.com:jgshort/tegen into test-suites