Adjust dashboard colours

Problem/Motivation

The Drupal CMS dashboard colours are not all set correctly with xClaro.

Proposed resolution

• Use a distinct CSS file and library name.
• Load the library (CSS) only on the Dashboard pages (view and edit).
• Add the proper CSS declaration to make the dashboard more dark friendly.
• Remove rounded corners and style it like the Status Report, including block headers.

Note that the issue is not Drupal CMS specific. Any module pages displayed in dark mode may need some overrides.