add an install command

[lsmith77]

take inspiration from https://github.com/Sylius/SyliusInstallerBundle/blob/master/Command/InstallCommand.php

[cordoval]

nice is this to plug crm automagically?

[lsmith77]

another stretch goal for 1.3

[wouterj]

Let's make this a nicetohave. I think this can be quite nice, but maybe more as a standalone CmfSetupBundle/CmfDistributionBundle.

Another great example of such commands: https://bundles.kunstmaan.be/documentation/installation

[dbu]

i removed the milestone. i don't think its a trivial thing, and indeed fits better in some separate bundle. not everybody will want this in their project.

[dbu]

something can be done with flex.

also, we stopped maintaining several of the components, so a cross-bundle installer is less important now.