Allow detection of project with a Maven reactor using a config property

[DirkMahler]

Currently Maven reactors are treated by default as a project with a single store and databases.
This can be switch to the legacy behavior to detect projects within a reactor by disabling the config setting use-execution-root-as-project-root. In this case the modules are scanned for the existence of jqassistant folders which are used as markers for project roots.
It shall be evaluated if the property can be deprecated and replaced by another config setting within a module. It would mark a module and its sub-modules as a project avoiding the need of the jqassistant folder. This should make the scope of projects more transparent to the user.