Rule priority can be only set from 0 to 7

[ejhernandez@…]

If there are more than seven rules attached to an interface, the priorities of the rules which are the seventh or more are equal. Thus, the table position is quite misleading if there are more than 7 rules.

This ticket is intended to provide a solution to this issue. There are several options to take into account:

1. Stay the same, setting a warning message when the eighth is added.
2. Set the priority (0-7) when adding a rule is done
3. More suggestions here

[ejhernandez@…]

The rules are grouping per priority setting/editing the priority per rule

[ejhernandez@…]

(In [6964]) Changing model to add priority as a way to tailor ordering and the changes related to the module refs #447

[ejhernandez@…]

(In [6968]) Making orderable more realistic refs #447

[ejhernandez@…]

(In [6970]) Setting a new way to get the lowest priority and checking service correctness typing refs #447

[ejhernandez@…]

(In [6971]) Fixing some bugs related to undef and empty strings. Now it correctly order per priority closes #447

[ejhernandez@…]

(In [6972]) All unit test are now passed refs #447