initial version of msg to uorb script

Standard and embedded types work, may need small refinements for some
types

msg/std_msgs/MultiArrayLayout.msg

@@ -0,0 +1,26 @@
+# The multiarray declares a generic multi-dimensional array of a
+# particular data type.  Dimensions are ordered from outer most
+# to inner most.
+
+MultiArrayDimension[] dim # Array of dimension properties
+uint32 data_offset        # padding bytes at front of data
+
+# Accessors should ALWAYS be written in terms of dimension stride
+# and specified outer-most dimension first.
+# 
+# multiarray(i,j,k) = data[data_offset + dim_stride[1]*i + dim_stride[2]*j + k]
+#
+# A standard, 3-channel 640x480 image with interleaved color channels
+# would be specified as:
+#
+# dim[0].label  = "height"
+# dim[0].size   = 480
+# dim[0].stride = 3*640*480 = 921600  (note dim[0] stride is just size of image)
+# dim[1].label  = "width"
+# dim[1].size   = 640
+# dim[1].stride = 3*640 = 1920
+# dim[2].label  = "channel"
+# dim[2].size   = 3
+# dim[2].stride = 3
+#
+# multiarray(i,j,k) refers to the ith row, jth column, and kth channel.