Added StandardDeviationKeyVal operator and test class.
SPOI-1182 -

Added the Filter operator that can filter the key-value pairs based on the given filter. The keys in the KeyValuePair has to be implement a Filterable interface.

Also added required test cases.
Merge branch 'SPOI-1182'
fixed a typo and reorganized imports.
Merge branch 'master' of github.com:DataTorrent/Malhar
removed misleading comment.
Fixed warnings related to raw type and useless System.out.println statement.
removed unused imports.
Cleaned up the LocalFSInputOperator so that the duplicate functionality is removed.
Merge branch 'master' of github.com:DataTorrent/Malhar
Merge branch 'master' of github.com:DataTorrent/Malhar
Merge branch 'master' of github.com:DataTorrent/Malhar into my_master
Merge branch 'master' into my_master
db interface redesign
store should not be transient to preserve connection parameters
removed passthru properties
removed passthru member
added javadoc for abstract functions
Store is now a generic
Store is now a generic