Adding json file for M4 model broken into parts and arranged by hierarchy.  Hierarchy is read from a master collada file, however parts must be manually saved out - that part isn't scripted yet.     Also added jwriter.py to the scripts directory, and libfind.py which jwriter.py loads as a module.
Note that  M4_Carbine_grouped.json  may have errors.  Currently, jwriter is not written to add commas between siblings in the json file, so this Could Be Better