Remove .action-link and button-link css (#5370)

### Requires:

- https://github.com/Icinga/ipl-web/pull/284 (ipl-web v0.12.0)

public/css/icinga/main.less

@@ -7,10 +7,6 @@
 // Width for the name column--th--of name-value-table
 @name-value-table-name-width: 38/3em;
 
-.action-link {
-  color: @icinga-blue;
-}
-
 .error-message {
   font-weight: @font-weight-bold;
 }
@@ -127,22 +123,6 @@ a:hover > .icon-cancel {
   .fg-stateful();
 }
 
-// Link styles
-
-.button-link {
-  .action-link();
-  .rounded-corners(3px);
-
-  background: @low-sat-blue;
-  display: inline-block;
-  padding: 0.25em 0.5em;
-
-  &:hover {
-    background: @low-sat-blue-dark;
-    text-decoration: none;
-  }
-}
-
 // List styles
 
 .comment-list {

public/css/icinga/mixins.less

@@ -61,13 +61,6 @@
           transform: @transform;
 }
 
-.user-select(@user-select) {
-  -webkit-user-select: @user-select;
-  -moz-user-select: @user-select;
-  -ms-user-select: @user-select;
-  user-select: @user-select;
-}
-
 .transition (@transition) {
   -webkit-transition: @transition;
      -moz-transition: @transition;