Bugfix: Unreliable imports.

This MR finalizes #112 by fixing an unexpected global package-import instead of a local minifflask module.

Description

From #112 on, miniflask tries to use pythons import statement if possible to load modules.
The solution was to import the module name using the importname, i.e. without the module-base-directory in its identifier. Interestingly, this indeed loaded the correct modules in most cases.
However, in case a system-module with that name exists, miniflask would load that instead of the local module.

Setup:

1. Install any python package under the name setup.
2. Run pytest.

Problem:
Due to a module under ./tests/event/beforeafter/modules named setup, the setup above will result in an error.

Things done in this MR

The solution is quite simple: the module-id actually contains the base-directory name (in case the module directory has not been named otherwise in the mf.init-call - thus the string is correct in exactly those cases in which we want the internal import to be used.

There is one special case, that needed to be resolved to make this work consistently:
The miniflask-internal modules settings, events, modules, etc. have been placed in miniflask/module/*, but have been referenced using miniflask.* instead of miniflask.module.*. To make things consistent, this MR moves all those modules directly into the miniflask base directory.

Check all before creating this PR:

• Documentation adapted
• unit tests adapted / created