TASK: Allow installation on Neos 8.x

In addition Neos dev-mater is allowed aswell.

Merge pull request #73 from kdambekalns/bugfix/self-return-type-php73

BUGFIX:  Avoid fatal error on PHP 7.3

Merge pull request #70 from daniellienert/bugfix/remove-AssetExtracto…

…rInterface-object-config

BUGFIX: Remove object config for AssetExtractorInterface

Merge pull request #68 from daniellienert/feature/make-suggestionCont…

…ext-configurable

FEATURE: Make suggestion context configurable

Merge pull request #65 from daniellienert/bugfix/fix-suggestion-context

!!! BUGFIX: Contexts are respected in a multi-site environment.

Merge pull request #60 from Flowpack/task/change-sanitation

TASK: Use more fine-grained sanitation

TASK: Merge branch '4.0' into master

# Conflicts:
#	Classes/Controller/SuggestController.php

TASK: Remove wrong result example

Merge pull request #49 from aertmann/master

BUGFIX: Make completions/suggestions work with ES 5.x

TASK: Configure compatibility for Neos 5.0 / Flow 6.0