Move to phive to install dev toolings

[shochdoerfer]

We should make use of PHIVE to install dev toolings like phpstan, phpdocumentor, php-coveralls.

[heiglandreas]

I'm currently more inclined to use tm/tooly-composer-script as

1. that is configured using the already used composer.json (so one config file less in the already cluttered main directory)
2. it can load all required tools and not a subset of tools that the folks of PHIVE have whitelisted (OK. Phive seems to be able to install any tool using a fixed URL, but then it's not better than curl, so why use another tool. And signature-validation then has to be done manually)

Verification against a signature is done by both tools.

And in combination with the getlatestassets-API it is possible to specify exactly which version of the tools you explicitly want for tools that have their releases hosted on github.