UI: Enable CSS use in mistral dashboard

* Removed non-working implementation of LESS (scss to css compiler)
* Removed redundant unused styles
* Added CSS support - the same way they do in Murano Dashboard
* We could always add LESS and Django intergration later,
  seems it only works in static folders inside the Horizon respository ATM.

Closes-Bug: 1512377

Change-Id: Ic1f239c103382e780df754ff8fac4b6374ef33cb

mistraldashboard/default/templates/default/base.html

@@ -3,5 +3,5 @@
 
 {% block css %}
   {% include "_stylesheets.html" %}
-  <link href='{{ STATIC_URL }}mistraldashboard/scss/style.scss' type='text/scss' media='screen' rel='stylesheet' />
+  <link href='{{ STATIC_URL }}mistraldashboard/css/style.css' type='text/css' media='screen' rel='stylesheet' />
 {% endblock %}

mistraldashboard/static/mistraldashboard/scss/style.scss

@@ -1,19 +0,0 @@
-.codeblock {
-    position: relative;
-
-    .short {
-        cursor: pointer;
-    }
-
-    .full {
-        display: none;
-    }
-
-    &:focus .short {
-        display: none;
-    }
-
-    &:focus .full {
-        display: block;
-    }
-}