New path format

[klermonte]

Insted file path style use object notation:
/header/blocksCount => @root.header.blocksCount or just header.blocksCount
./blocksCount => @parent.blocksCount
suggest new types of path parts:

• @parent - select parent of current field
• @prev - select previous sibling
• @root - select root of DataSet, optional, just for clarity e.g. @root.header and header are equal