Removed quotation layer for one-liner examples

The quotation was intended for helping creating example descriptions, but
it turned out that the matcher message could just as well be used, so the
quotation was just an unnecessary layer.
Removed PowerPack.Linq dependency

The PowerPack.Linq dependency was used to evaluate code quotations for
matcher expressions. Now that quotations are out of the loop, the
PowerPack.Linq package is no longer used.
Added ShouldNot one liner expressions