Add the special pattern "<...>" for use in the target pattern.

This change relates to the question:
https://answers.launchpad.net/graphite/+question/218717

Basic summary:
The new pattern corresponds to a match-all up to an arbitrary depth.
This is equivalent to the * wildcard character zero or more times.
E.g. a.b.<...>.c.d will match a.b.c.d, a.b.1.c.d, a.b.c.1.2.3.c.d, etc.