TableScanOperator should be blocked until split is added

Also, TableScanOperator needs to delegate isBlocked behaviour to its data source
to gurantee the same call procedure with ScanFilterAndProjectOperator
Add SPI documentation
Add REST API documentation and overview of Presto
Add documentation for HAVING and GROUP BY clauses
Add intToLong
Improve aggregation compilers

Generate byte code for entire Accumulator classes, also refactor the
verification logic to separate it from the compilation
Add getTypes to TypeManager
Add getTypeManager to Metadata
Add support for compiling accumulator that need to see nulls
Implement MAX_BY