Limited item display and Load More and Load Previous implementation

- showing upto X items and loading 3 more items done in first commit
- showing from X to X+2 and moving to X-2 to X on Load Prev and moving to X+2 to X+4 on Load More is part of the second commit

QUERIES -
- $scope.phones assignment is moved inside the passed function to Phones.query(), have questions regarding this !!!

THINGS NOT TAKEN CARE OF -
- Animations do look wierd on either of the actions
- Behavior with filters has not been given thought upon