Add getVersions method to the SDK/API

`get_versions (input_CID, [wallet_addresses])`
input_CID can be any data structure (asset, type, function, pipeline)
wallet_addresses is a set of addresses you trust to re-version
if empty, only return your versions
if not empty, check for clones of this asset
Returns array of CIDs of new versions, you can filter to get the most recent one