Command autoloading feature

This PR actually mix with 3 stuffs.

  - Command autoloading feature
  - A bug fix when throwing an ExecuteMethodNotDefinedException
  - make ProgramName of an Application be its sufficient part of $argv[0] only

I can re-organize it if you want.
Since you're using `scandir`, using  `scan` as the prefix is more readable.

`readXXX` sounds like opened some files and read some contents.