po2prop: expand test

Expand the test to two units to try replicate issue in bug 115.
fn tests: po2prop using bug 115 example

Created a functional test for po2prop using the example from bug 115.
This was not an issue it seems but we now have a test for --personality.
po2dtd: improve test readability
po2prop: add missing accesskey test
po2prop: use the source language accesskey if translations is missing

Fixes bug 115 comment 6