Make host flows only accept canonicalized host names as input

This now throws errors when a non-lower-cased, non-puny-coded, or non-canonicalized host name is passed in as an input parameter.

The approach we'll take is to first notify registrars which hosts we'll be renaming, then
issue EPP host update commands to effect those renames as superuser, then push this code
live to production.

This fixes #38 on GitHub.

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=138441130

java/google/registry/flows/host/HostCreateFlow.java

@@ -65,6 +65,9 @@ import org.joda.time.DateTime;
  * @error {@link HostFlowUtils.HostNameTooLongException}
  * @error {@link HostFlowUtils.HostNameTooShallowException}
  * @error {@link HostFlowUtils.InvalidHostNameException}
+ * @error {@link HostFlowUtils.HostNameNotLowerCaseException}
+ * @error {@link HostFlowUtils.HostNameNotNormalizedException}
+ * @error {@link HostFlowUtils.HostNameNotPunyCodedException}
  * @error {@link HostFlowUtils.SuperordinateDomainDoesNotExistException}
  * @error {@link SubordinateHostMustHaveIpException}
  * @error {@link UnexpectedExternalHostIpException}