parse_isotime filter to parse a date string.

This then allows the resulting date value to be piped
to one of the standard django date/time format filters

This is identical to oslo timeutils parse_isotime, but annotated with
@register.filter

Required for blueprint: heat-ui

Change-Id: Ibecca77d50bb5c0df59e07e9572069215229f60a

tools/pip-requires

@@ -5,6 +5,7 @@ pbr>=0.5,<0.6
 Django>=1.4,<1.6
 django_compressor
 django_openstack_auth>=1.0.8
+iso8601>=0.1.4
 netaddr
 python-cinderclient>=1.0.2,<2.0.0
 python-glanceclient<2