URI -> IRI

Replaced URI/URL with IRI/IRL.

Did not replace reference in version history (since 0.95 specififed URI).
Also did not replace "mailbox URI" or "openid URI", since these are defined to be URIs by other standards.
mailto URI -> mailto IRI

Based on @fugu13 's comment, also changing mailto URI to IRI.
Removed line about URI encoding since it no longer applies
Merge pull request #322 from bscSCORM/IRI

URI -> IRI