Allow to override phpci.yml configuration per build

[corretge]

Sometimes we need to create a build that is not using the default PHPCI configuration loaded from phpci.yml file in the repo.

Now, the per-project configuration is loaded only if the phpci.yml file is not present in the repo.

I propose to change the order:

• If exist per-project config, load it.
• If not, load the repo file.
• If not, defaults.

I usually have more than one PHPCI project per repo: The full build, the only phpunit check, the only phpcs&phpmd check, etc...

[DamirPecnik]

+1