Allow to add user-defined labels to SCL files in the database

[JakobVogelsang]

As a user of CoMPAS I want to add labels to SCL files I store in the database. Those labels shall allow for better filtering of the files as described #184

Requirements

• allow adding up to 20 labels
• make sure that labels follow pattern: [A-Za-z][0-9A-Za-z_-]*
• allow removing labels

Depends on

• name space extension to save labels to the SCL see Issue

Mockup

hint: the icons in the model are from the goodle library: label and new_label

Additional information
The labels are added/removed to/from the private section in the SCL File in the front-end. The Data Service just saves the SCL File and won't change the anything to the labels. The Data Service only uses the labels when retrieve the list of SCL File stored in the database.

Example how the private section should look like. Check if the namespace needs to be added to the SCL Element.
And the type of the private section will be 'compas_scl'. See Locamation Plugin how to work with private extensions.

<SCL xmlns="http://www.iec.ch/61850/2003/SCL" xmlns:compas="https://www.lfenergy.org/compas/extension/v1" 
          release="4" revision="B" version="2007">
  <Private type="compas_scl">
    <compas:SclName>MiniGrid</compas:SclName>
    <compas:SclFileType>CID</compas:SclFileType>
    <compas:Labels>
     <compas:Label>Label1</compas:Label>
     <compas:Label>Label2</compas:Label>
    </compas:Labels>
  </Private>
  ...
</SCL>