Add library app (fix #7 #10)

Ref: #7 #10

This only adds the basic logic of the app. More to come in other PRs :)
```
/home/ybon/Code/py/ideasbox/library/forms.py:6: RemovedInDjango18Warning: Creating a ModelForm without either the 'fields' attribute or the 'exclude' attribute is deprecated - form BookSpecimenForm needs updating
```
Damn :)
But I thought the suggestion was to create a form for each model and to add fields to this form, but now I understand: we are only talking about adding fields (or exclude) to the form we have created.
I'm doing it :)