Allow string concatenation with the the Option's symbol

[Alexangelj]

Each ERC-20 option has the same symbol: "PRM". These can be improved by adding prefixes which represent the option and the underlying assets.

For example, Long options could be prefixed with "l" and short options prefixed with "s". Then, WETH long options would have the symbol "LWETH". Maybe, include put/calls as well?

Right now, calls are implied if the option has a baseValue of 1. Puts are implied by having a quoteValue of 1. Maybe make this clearer in the option symbol.