feat: wallet configuration

[nicosantangelo]

Allows for an array of Wallet instances to be used by eth.connect. Example: https://github.com/decentraland/marketplace/pull/195/files#diff-42d52283afaced49eb9838e53b7d1891R18

Sorry if the PR goes a little out of script, fixing a param on the docs and removing a method, but I thought it might be easier to add it here. I can revert the commits.

Related:

• https://github.com/decentraland/marketplace/pull/195
• https://github.com/decentraland/commons/pull/66