Disable FrontendBundle

[solverat]

Q	A
Bug report?	no
Feature request?	yes
BC Break report?	no
RFC?	no

Something like:

coreshop:
    frontend: false

This would allow us to reduce the platform stack, if a project does not require any frontend functionality.

[dpfaffenbauer]

we're actually playing with the idea to remove the frontend bundle completely from coreshop/core-shop and moving it to a separate bundle

[dpfaffenbauer]

We will not remove the bundle completely, we will just disable it by default. We need the bundle in the core for the frontend tests, which are a crucial part of our testing strategy.