Format of epsilon symbol from lt-print

This is a bit bikeshedding, but I think that we should change the epsilon symbol in lt-print from `ε` either to `<ε>` or to `@0@`. It probably needs to change if we're ever going to deal with Greek, although it's very low priority.

My feeling is that `<ε>` is more Apertiumy. This could also be updated in HFST's `hfst-txt2fst` tool so that the `-e` option is not necessary.