Introduce standard paths for included libs, plugins, imports in AM packages

When developing a more complex app which needs to be packaged for ApplicationManager you alwasy need to define certain extra things, like the importPath or pluginPath.

In addition a rpath needs to be used to be able to resolve packaged libraries inside a package.

Because this is complicated, it would make sense to define some standard pathes which work without additional configuration e.g.

• The "imports" folder is automatically added to the QML2_IMPORT_PATH
• The "plugins" folder is automatically added to QT_PLUGIN_PATH
• The "libs" folder is automatically added to LD_LIBRARY_PATH