Fix MAGN-1967; Clean up some AST nodes

Fix MAGN-1967: Number nodes with range syntax no longer work;

Cleanup IntNode, BooleaNode and DoubleNode:
1. Rename property value to Value
2. Change the type of Value from string to the corresponding type of node (int, double or boolean), so that when creating these node we don't need to send string value, and don't need to parse the string value when try to get literal value.