Enable to run the application closer to the production environment

Having the description field only on the Model class makes things
inconsistent.
It's nice to have a description on other attributes as well.

The generation of the QR code image is quite slow and makes the page
displaying them take a long time to load when it includes more a few.
The data never changes and can easily be cached (the repr() of the class
is used in the cache key, so if the name or id changes, the cache will
be recomputed - there is no need for a timeout).

Column not visible but searchable.
Allow to search comments and TAG number for items imported from JIRA.

One should be able to enter a MAC when creating/editing an interface.

See https://github.com/showdownjs/showdown/wiki/Extensions

Allow to scan a label to enter an ICS id via the web interface

The user_id is used to track the item creator. It's not supposed to be
updated afterwards. There is no need to track changes.

uwsgi is used to run the application in production.
It was lost during some environment updates...

Strings are automatically converted to datetime object.
Note that datetime are stored without timezone in the database (in UTC).

text is really generic and could conflict with another variable.
body is often used for comments.

Required to create users when importing items from JIRA.

Renamed blueprint from "users" to "user" to be consistent with other
blueprints (inventory and network).

+ fix tests

This allows to easily register items via the API without giving an ICS
id.

Split API in different blueprints like for the web UI:
- users (login)
- inventory
- network

Use version in API url (api/v1) to make future changes easier without
breaking backward compatibility

- This will help tracking who and what was created / changed
- Move fetch_current_user_id to utils.py
- Make ItemComment inherit from CreatedMixin

- Only admin should be able to create networks
- Deleting an interface should require at least create group (should
  that be restricted to admin?)

Add delete and delete-orphan options to the cascade behavior:
- delete: delete from database associated cnames when deleting an
  interface
- delete-orphan: delete cname when removing it from the list of
  interface.cnames

Allow to create/delete cnames when creating/deleting interfaces

Move regex to validators.py

Used to validate a list of strings against a regular expresssion.

Create macro to add delete button with modal dialog
to cancel or confirm deletion.

To check if the unique object is the one being edited, we need to store
the object used to create the form in the form (_obj).
This is inspired from flask-admin.

Use inheritance to avoid duplication

cellspacing="0" : to avoid double lines in the header
width="100%" : to have extra fields (search, paging...) aligned properly with
the table

When registering a new host, only admin users shall be able to select
networks marked as "admin_only"

A gateway should be an interface like any other IP.
Use tag to identify it.

It shouldn't be possible to change the ICS id of an item.
But when registering a bunch of existing items via the API, we need to
allocate an ics_id otherwise not much can be done in the interface.
The id is required for the view and edit page.

The solution is to define some "temporary" ids that don't correspond to
any pre-printed labels.
Items with a temporary id can be assigned a real ics_id when assigning a
label.

Reserved ids start with 'ZZ' (from ZZA000 to ZZZ999)

ICS id can now be non nullable.