Contribution importer does not handle currency symbols

If the amount in a column is something like "$25.00", then the import preview shows this value, so you think it will work. However, when the important is actually performed, while there are no errors, all of the amounts preceded by a dollar sign end up being imported as 0.00.

Either the importer should throw an error (annoying but better than silently doing the wrong thing) or better yet, it should strip currency symbols from the head and tail of the string. I believe that in some countries they commonly use space around the symbol, so that should be stripped too.