Change key binding compile project action

C-c is common prefix that should be reserved for users. We should bind
compile action to something else, like M-c.
Fix error when Projectile fails to get sub-project files

When external command for getting sub-project files fails, it should not
break Projectile. Simply fall back to the default behavior.
Merge pull request #484 from tuhdo/master

Change key binding compile project action, fix external command error and add new action to create virtual directory