Resolve "Complete state vector new data structure?"

Closes #287 (closed)

demos/hello_wolf/yaml/hello_wolf_config.yaml

@@ -11,8 +11,14 @@ config:
     dimension:            2               # space is 2d
     prior:
       mode:               "factor"
-      state:              [0,0,0]
-      cov:                [[3,3],.01,0,0,0,.01,0,0,0,.01]
+      # state:              [0,0,0]
+      $state:
+        P: [0,0]
+        O: [0]
+      # cov:                [[3,3],.01,0,0,0,.01,0,0,0,.01]
+      $sigma:
+        P: [0.31, 0.31]
+        O: [0.31]
       time_tolerance:     0.1
     
   sensors: