Add CLI command to display all addresses of used contracts

[hswick]

This would be useful to verify addresses or help other developers more easily integrate TrueBit. I'm thinking it could look like this

Command: contracts

Output:

Incentive Layer: 0x123423423423
TRU Token: 0x21134234234234
Filesystem: 0x13234234234
Dispute Resolution Layer: 0x123234234234