added new constraints as per Hernan's suggestions... Also changed the text/description of the constraints to be coherent.. extended the mira.ecore to have new constraints implemented. Added new constraints are 1) CheckListReviewConstraint (to check if the checklist attached with every requirement), 2) RequirementExistsConstraint (to check if the Requirement Package has the requirement) and 3) ComponentExistsConstraint (to check if the Component Architecture has components available).