This came up on the mailing list.
yyyy-mm-dd (ISO 8601) is the internationally accepted format for numeric
dates. This commit changes all BIPs to use that instead of dd-mm-yyyy.
It also updates BIP 0001 to prescribe the new format.
Empty addresses should be valid for compatibility with BIP 72.
Empty query parameters should also be valid, since they are harmless,
and clients already accept them.
With these changes, bitcoin:?& would be a valid (but useless) URI.
The "bitcoin:" URI scheme needs to be case-insensitive according to the RFC,
but the query parameters should be case-sensitive according to the bitcoin-qt
client implementation.
The URI syntax uses an ampersand to separate query parameters,
but the ABNF grammar didn't reflect this fact.
Also, the type of grammar used here is "ABNF" and not "BNF".
