(three commits) add € sign, give CSA layout better name, trim unneeded key types, and drop two symbols

The first patch adds the missing € symbol to the Canadian CSA standard layout, and gives this layout a more recognizable name (for Canadians).

The second patch trims some unneeded key-type definitions, and adds two missing ones.

And the third patch removes two symbols from positions that don't conform to the CSA standard. (It doesn't remove all non-conforming symbols to not inconvenience people that, in the past seventeen years, have gotten used to having them also in their legacy positions. The affected two symbols can be removed because probably no one uses ¤, and people who use ¬ can probably appreciate strict logic: each symbol in just one place. :) )