[FEATURE] Extension:list command

This Introduces a new commandController action for listing all available extensions.

Usage:

```
php typo3/cli_dispatch.phpsh extbase help builder:list

Lists installed Extensions. The output defaults to text and is new-line separated.

COMMAND:
  builder:builder:list

USAGE:
  ./cli_dispatch.phpsh extbase builder:list [<options>]

OPTIONS:
  --detail             If TRUE, the command will give detailed information such
                       as version and state
  --active             If TRUE, the command will give information about active
                       extensions only
  --inactive           If TRUE, the command will give information about
                       inactive extensions only
  --json               If TRUE, the command will return a json object-string
```

Please note that, as JSON is mostly used by machines, json output allways implies
--detail to be TRUE regardless of its setting.
Merge pull request #12 from cedricziel/listExtensions

[FEATURE] Extension:list command
[FEATURE] Add minimal composer.json
Merge pull request #14 from cedricziel/composerInit

[FEATURE] Add minimal composer.json