added lab4
Merge branch 'master' of https://github.com/michaelghay/cosc460

Conflicts:
	mysimpledb/src/java/simpledb/Aggregate.java
	mysimpledb/src/java/simpledb/IntegerAggregator.java
	mysimpledb/src/java/simpledb/StringAggregator.java
Lab 4 TableStats Test passes!