Azimuth example with angles of azimuth and my drawing cheatsheet...

Azimuth example with angles of azimuth and my drawing cheatsheet (st_azimuthmath.sql) in case have to do this again.

git-svn-id: http://svn.osgeo.org/postgis/trunk@7011 b70326c6-7e19-0410-871a-916f4a2858ee