Add confirmation dialog to change VRRP address.

This patch causes a confirmation dialog to rise when change VRRP
address button is launched.

To achieve that, this patch changes the class of the button to button_confirm,
where confirm dialog logic is already implemented.
Add progress bar to all confirm buttons.

All buttons asking for confirmation show a progress bar if confirmation is given.
Progress bar is displayed until the background call finishes.
Change default addressing in mp-vcpe.

Interfaces connecting LRs between each others should have a different network than the rest. Each lt link should have its own network.
Merge pull request #544 from jordi-puig/develop

 The GUI application get the list of vcpe's from session.
Avoid null poiter exception in isFreeVRRPGroup.

MP-vcpes don't have VRRP configuration (it's set to null), so
calling isFreeVRRPGroup when there is a MP-vcpe already created
launches a nullpointer exception.

This patch fixes this by checking vrrp configuration and group is
not null before trying to compare it.
Merge branch 'develop' of git://github.com/dana-i2cat/opennaas into feature/confirm-and-progress-bar-in-gui-buttons
Merge pull request #543 from isartcanyameres/fix/mp-vcpe-default-net-addressing

Change default addressing in mp-vcpe.
Merge pull request #545 from isartcanyameres/fix/null-in-isfree-checker

Avoid null poiter exception in isFreeVRRPGroup.
Merge pull request #546 from isartcanyameres/feature/confirm-and-progress-bar-in-gui-buttons

Feature/confirm and progress bar in gui buttons
Merge branch 'develop' of git://github.com/dana-i2cat/opennaas into develop
Add titles in some vcpe pages