Possible fix of selector, now using 3 LUTs.

Changed the selection, most notably to have ab-semantics be
'at least one valid '1'-vote'. Should use 4 LUTs in my head,
but ISE optimizes it to use only 3... Would be good to understand
how it does this, and whether there is any logical interpretation
of the synthesized result since we then should alter the VHDL to
something simpler.

Also tried to complete the "standard operation" test case, and
added a few regression tests. The test cases are by no means
providing a thorough coverage atm, however...

Next steps: Add more test cases of voting, specific tests for
corner cases of ecc generation, and try to optimize the ecc
machinery while keeping the tests passing.