Add support for `order` in phases

[vikasrohit]

We need to support the order for each phase. Initially, it would be an optional field and would be set only for new phases created after this change.
Cases where we need to update the order of the other phases in the same project:

1. when a phase has change in order field while updating a phase
2. when a new phase is added with order field and there exists at least one phase at or after that order

Also, do let us know if you think there is another case(s) where we need to cascade the changes of the phase's order. We are doing similar stuff for milestones and milestoneTemplates.

NOTE: Changes should be backward compatible i.e. should not cause any interruption in existing functionality when phases do not have order field.

[vikasrohit]

Closing. Working okay as per current requirements. We are not using order field any where while consuming the api, this was just for future features.

@gondzo Please feel free to tag it as per convenience for payments.