Added almost all params, made front API usable, and added crs transform draw testing.

Next step figure out more stable proj4 parsing of datums and proj etc,
with adding more specific names.
Then consistently make to_esriwkt work.

pycrs/projections.py

@@ -8,3 +8,7 @@ class UTM:
     proj4 = "utm"
     ogc_wkt = "Transverse_Mercator"
 
+class ObliqueMercator:
+    proj4 = "omerc"
+    ogc_wkt = "Hotine_Oblique_Mercator"
+