Update wfArrayToCGI and wfCgiToArray:

Update wfArrayToCGI and wfCgiToArray:
- 'foo' => '' now outputs "&foo=" instead of the key being omitted
- 'foo' => null and 'foo' => false now omit the key instead of outputting "&foo="
- Added a test to make sure that 'foo' => true outputs "&foo=1"
- Fixed a php notice caused when passing a =value-less bit like "&qwerty" to wfCgiToArray by treating it like php and extracting it as 'qwerty' => ''
- Updated tests