Add alwaysfail, and authandfail

[abourget]

This contract would be even better fit for these patterns.

See https://github.com/EOSIO/eosio.contracts/issues/169 for previous discussions

If you think it would be acceptable, I'll submit a PR.

[abourget]

Issuing an inline action to an account with an ABI would allow structured data to be exported, read through the always failed traces, like @tbfleming suggested in the thread above.

[tbfleming]

We're working on a proposal to formalize sending notifications to eosio.null. The assert-to-save-costs approach is controversial internally.

[abourget]

What is an assert-to-save-costs?

[tbfleming]

If it doesn't assert, then the user will be charged for the query. The main objection is using the transaction execution system, with all of its overhead, to answer queries.