[task/sami] Add sami/sami as a composer development dependency.

PHPBB3-12495
[task/sami] Replace phpdoctor with sami.

PHPBB3-12495
[task/sami] Also ignore ext/ directory.

PHPBB3-12495
[task/sami] Establish alphabetical order.

PHPBB3-12495
Merge pull request #2470 from bantu/task/sami

[task/sami] Add Sami to composer dependencies and build script

* bantu/task/sami:
  [task/sami] Establish alphabetical order.
  [task/sami] Also ignore ext/ directory.
  [task/sami] Replace phpdoctor with sami.
  [task/sami] Add sami/sami as a composer development dependency.