sort iterator basic function already done!!!
print and the projectionIterator for the variable class is ok!!!
filter and scan can be supported by variable schema and blockstreambase
begin to write the hashtable2 supported by variable version
project physical iterator
a funciton point to support the project!!!
add the doc which contains some images and documents.
change the image to jpg.
change the image to jpg.
can do a a+b-1, a-b+1 at the physical level.
project and sort.
project logical operator can be done.
project logicalOperator successful!!!
double can't be supported well.
Merge branch 'casa'

Conflicts:
	.cproject
	.project
	Test/TestMain.cpp
	common/ExpressionCalculator.cpp
	common/ExpressionCalculator.h
	common/ExpressionItem.cpp
	common/ExpressionItem.h
	common/Expression_item.cpp
	common/TypeCast.h
	common/functions.h