rtt_rosparam: It is not possible to unmarshall nested array

[Hugal31]

#162 allows to unmarshall any custom sequence property type using property decomposition. However, it appears it doesn't work on nested arrays.

After some investigation, it seems it goes like this for a vector<vector<int>> when converting it from xml to orocos property:

• The array of array property is decomposed into a rosbag in xmlParamToProp.
• The elements are then recursively sent to xmlParamToProp.
• However, the elements are now it the PropertyBag form, and loose the link to their type info. This prevent the function from detecting a sequence.

I may try to fix this if I find some time to work on it.