many transactions with empty operations are confusing

[pro-wh]

to someone exploring the API, having most transactions right now be unmodeled node registrations (or something) might seem like they aren't getting transaction info right.

some ideas to address this:

1. document it
2. add something to the transaction so people know it's intentionally blank. maybe some metadata item
3. are we allowed to put the raw transaction in the metadata?

[PrernaPadhee]

what all transaction types are expected to have the operations field populated ?

[pro-wh]

we recommend that you look for operations in all transaction types