Update NSL xor tests

Put the most realistic scenario in nsl.api, keep helpers in nslhelp.api as
tests. Also add NSL-xor-1a.api, a variant which I had in stock.

All these tests pass with the current version of akiss, in a minute or so.
Accept multiple tests as multiple arguments
Review and cleanup KCL related tests

Removed some duplicate tests, moved all KCL tests to examples/rfid/KCL*. All
those examples pass with the current version.

Removed comments regarding poor performance or redundant tests from several
examples, as these issues are fixed.

Left two degenerate examples in examples/tests, namely rfid0.api and
rfid0h.api. The former does not pass, or takes significantly longer than other
tests.