documentor, ecere/sys/json: Addressed various issues with new eCON docs

documentor, ecere/sys/json: Addressed various issues with new eCON docs
- Was using uninitialized local char array as index into cache!!
- Fix use of freed memory:
   - Updating time stamp on doc access (getDoc() could previously delete the 'doc' it returns in the pruning at the end)
   - Making use of instance reference count so as to keep one reference for the cache, and one for the returned doc
   - Freeing returned foc in ReadDoc()
- Fixed 'clearing' of descriptions (Was refusing to save 'empty' changes)
- Clearing empty MethodDoc and FunctionDoc
- Avoiding to save empty class doc and namespace doc
- Fixed bad access of '_class' member on non 'class' types