Form doc-relative action fix, app-relative URLs

Document-relative URLs for submitForm now fixed, and added test code.

Moved 'basePathWithSubdir' test to TestsForBrowsers since it doesn't
make sense for Frameworks and was causing a 'risky test' message.

Updated PhpBrowser added amOnPage so it strips out leading
forward-slashes, making URLs app-relative for amOnPage.  Fixed test
code so it matched.