Docker: Update README instructions and tag the image correctly.

The new versions of Docker allow only [a-z0-9_] for the image tag and
won't accept uppercase letters.
Docker: Build using Ubuntu 14.04 LTS.
Project: Move PHP files to scripts/, update Dockerfile reference.
Scripts: Drop php.template file.

Use blocks in php.vim to perform substitution.
One file to rule them all!
Scripts: Update syntax script.

This commit throws away the old syntax file and adds a new one which
reads its configuration off a .ini file. The generated output is
slightly modified, but yields the same syntax file.
Scripts: Add block for last modified date and PHP version.
Syntax: Re-generate using PHP 5.5.12 and new script.
Syntax: Add ability to enable / disable built-ins for extensions.

Closes #9, Use a new variable to enable extensions.