Fix insert_tuple; Make Table::addRow branch specific; Fix bug in parser; Add delete logic in version_management;

Reset TableScan Operator's is_visible logical with the original; Adjust SemanticAnalysis to changes; Clone parent's columns in the _branchBitmap of every Table when creating a new branch

Add query tests; Make tuplestream operator handler function configurable in querycompiler; Register external functions used for version_management;

Add TupleStream as new physical root operator; Move methods of value transformation to seperate class

Add googletest framework; Modify interface of parser to seperate parsing from verifying; Add parser tests

Solve bug caused when inserting with a branch not existed yet; Solve bug caused by freeing tablealias string memory to early; Solve bug concerning visibility caused by not constructing branch lineage

Add version tag recognition for update statements; Solve bug caused by not checking if tuple is visible in Tablescan operator

Add version recognition for insert statements; Add version recognition for select statements; Modify TableScan operator to store the pointer to the alias; Modify version_management to take the version of the current table; free memory after using alias