Make the installer create the correct navigation items

We don't want separate backend navigation entries for add, edit, delete
actions. They all reside under index.
Other actions will get separate navigation entries

Fixes #29
Coding standards: PSR-2
Move message to their own class
Move questions to their own class
Move safe name generation to separate class
Coding standards: PSR-2
Major refactor, away from too much DIC, and towards real DI.

We're now using a Configuration object, that gets injected everywhere,
instead of injecting the whole depencency injection container.
This makes for a cleaner interface.
Generalize template variables in Forkmodule class

Fixes #31
Make the index page name label "Overview" instead of Index

Fixes #32
Fixes otherId for saving tags in update method
Calls delete method in delete action
Calls correct save method for action
Redirects after delete
Merge pull request #33 from jonasdekeukelaere/fix-update-method

Fixes otherId for saving tags in update method
Merge pull request #35 from jonasdekeukelaere/feature-call-save-action

Calls correct save method for action
Merge pull request #34 from jonasdekeukelaere/feature-call-delete-action

Calls delete method in delete action
Fix some errors in jonas' pull requests
Fixes labels, they don't need a capital first letter
Fixes underscores in translations
Merge pull request #37 from jonasdekeukelaere/fix-locale-installer

Fixes labels, they don't need a capital first letter