Crypto Conditions aren't part of the Interledger Protocol (ILP) any more

[ttmc]

Quoting from a blog post on the Interledger Blog:

6. The Cryptographer: Crypto Conditions
Died*: February, 2017. Age: 2 years.
Cause of Death: The features supported will be the least common denominator.
* Crypto Conditions continue to be developed at the IETF and used outside of ILP

One of the most thoroughly designed features that was ultimately left out of ILP was the Crypto Condition: a standard for encoding different signature algorithms and ways to combine them. A central primitive in the original Interledger design were the conditions used to hold and execute payments. We spent months developing a standard for this more flexible type of multisig, submitted it to the IETF, and then realized we did not need it.

The problem with having many condition types is that all intermediaries in a certain path would need to support the same algorithms in order for them to be usable. That meant that the only algorithms you could rely upon having support for would be the least common denominator. Most likely, this would come down to simple SHA256 hash-locks. Less than 20% of the functionality could serve more than 80% of the use cases, and so the Interledger standard parted ways with Crypto Conditions.

All docs (including the README) should be updated accordingly.