fix composer.json to allow easier installation

[fritzmg]

This PR provides the following changes:

• Removed symfony/framework-bundle dependency, since no component of this bundle is actually used. This enables easier installation of the extension in Contao >4.4.
• Added missing dependencies of actually used components.
• Removed leofeyer/optimize-native-functions-fixer dev dependency since that is already integrated in the PHP CS Fixer.
• Removed unused dev dependencies.
• Fixed indentation.
• Change license notation to its official format.

Unrelated question: why do you have your own ExceptionConverterListener? Is there any specific reason for that? Otherwise you should just simply throw all the Contao\CoreBundle\Exception\… exceptions directly.

[reluem]

Please merge this @hschottm. Your version of symfony/framework-bundle clashes with contao 4.8

[klimeckt]

@hschottm
Hi Helmut, jus upgraded my sites from 4.4 to 4.9.2 and cannot install the faqextensions. Is there any planning to upgrade this extension?
Best, Thomas