Update pom.xml

Increase xMx to 1024M 
OPAL-1682: Created a new widget for a column with checkbox and with a header that allow to select/unselect all items
OPAL-1682: Fixed warnings
Increase MaxPermSize for GWT
OPAL-1682: Removed commented code
OPAL-1682: Improved checkbox widget
OPAL-1706: Using the checkbox column widget for the indices
OPAL-1682: Improved checkbox widget
OPAL-1706: Using the checkbox column widget for the indices