Phpactor projectile root detection

[Sasanidas]

With this little change we can make phpactor be automatically aware of projectile root

[zonuexe]

@Sasanidas
What root can't be detected without projectile? Please explain why you need this patch.

[zonuexe]

@Sasanidas
The replacement by Projectile was applied to php-project instead of phpactor.el.
Enabling php-project-use-projectile-to-detect-root applies, to use projectile for Phpactor.
If you update php-mode and it doesn't work as expected, please let me know.

Thank you.