Add new LocalSecurityChecker

[Florian-B]

Add new LocalSecurityChecker (https://github.com/fabpot/local-php-security-checker) that replaces sensiolabs/security-checker (https://github.com/sensiolabs/security-checker)

[paras-malhotra]

There are several disadvantages of using local-php-security-checker including:

1. It is licensed under the AGPLv3. This means if your app uses local-php-security-checker, it has to be licensed under AGPLv3. This makes it literally useless in any commercial and non-AGPLv3 apps.
2. It includes binaries that depend on system architecture. So, this PR downloads the linux 386 binary but it will not work on other system architectures.
3. It cannot be pulled by Composer and needs shell scripts to pull it in

I have proposed an alternative PR here: #215

[zdenekdrahos]

Another disadvantage:

• adding local-php-security-checker is BC for existing users, and keeping old security-checker is confusing for developers