Support %p placeholder for project name in command strings

[bbatsov]

• All project command strings (configure, compile, test, run, install, package) now support %p as a placeholder that gets replaced with the project name at execution time
• The substitution happens in projectile--run-project-cmd so it works for both registered project type commands and user-entered commands
• Updated docstrings for projectile-register-project-type and projectile--run-project-cmd

Closes #1698

Example usage

(projectile-register-project-type 'my-docker-project '("Dockerfile")
  :compile "docker build -t %p ."
  :run "docker run %p"
  :test "docker exec %p make test")