Read node data from disk

add functions load in the document related class:
SuffixTreeNode, Document, Version
Add basic query processing
Add query processing in the node
Add Tree Node library in the query engine
Add Makefile to query-engine
Fix typo
Fix string bugs
Fix typo
Fix importing error
Fix typo
Add constructor to QueryVersion
Add public permission in QueryVersion class
Fix the private member
Fix BasicSuffixTree
Fix building bugs
Fix building bugs
Add feature to makefile
fix build_index bugs
Add install script
Add README