Create configuration_apps.rst

added description of apps configuration settings.
Update admin_manual/configuration_apps.rst
Update admin_manual/configuration_apps.rst

applied recommended changes how the apps path should be set.
Update admin_manual/configuration_apps.rst

changed writable status and added hint to separate shipped and downloaded apps.
Create configuration_3rdparty.rst

added a description of the 3rd-party settings.
Update admin_manual/configuration_3rdparty.rst

fixed a typo.
Update admin_manual/configuration_3rdparty.rst

changed quotes.
Create configuration_knowledgebase.rst

added description of the knowledge base settings.
Update admin_manual/configuration_knowledgebase.rst

applied smaller fixes.
Merge pull request #45 from j-ed/master

added description of the apps specific configuration settings.