Consolidate jQueryUI buttons into _buttons.scss

Fixes: CNVS-16353

- Moved jQueryUI button classes into main button
  components stylesheet, so we now have all button-related
  styles in a single place.
- Kept jQueryUI button set styles in their own
  stylesheet.
- Moved .Button disabled styles out of the canvas-button
  mixin because there was no longer any reason to make
  them part of the mixin.

Change-Id: I96d68efbb1fafc09e0d0d62c02eb886055da6434
Reviewed-on: https://gerrit.instructure.com/45354
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Colleen Palmer <colleen@instructure.com>
Product-Review: Colleen Palmer <colleen@instructure.com>
QA-Review: Anna Koalenz <akoalenz@instructure.com>

Author: Chris Hart

app/stylesheets/components/_buttons.scss

@@ -94,10 +94,9 @@ listen to the "click" and "keyclick" events and add tabindex="0" and role="butto
 ```
 */
 
-.btn, // <-- deprecated- do not use
+.btn,       // <-- deprecated- do not use
 .Button {
-  @if $use_new_styles { @include canvas-button(darken($canvas-neutral, 1%), $textColor, true); }
-  @else { @include canvas-button(darken($canvas-light, 3%), $textColor, true); }
+  @include canvas-button(darken($canvas-light, 3%), $textColor, true);
   border-radius: $baseBorderRadius;
   transition: background-color 0.2s ease-in-out;
   display: inline-block;
@@ -123,6 +122,12 @@ listen to the "click" and "keyclick" events and add tabindex="0" and role="butto
   // If not high-contrast, the "canvas-button" mixin has the :focus state share the same styles as :hover
   @else { &:focus { outline: none; } }
 
+  &.disabled, &[disabled] {
+    cursor: not-allowed;
+    pointer-events: none;
+    opacity: 0.5;
+  }
+
 }
 
 
@@ -180,9 +185,7 @@ listen to the "click" and "keyclick" events and add tabindex="0" and role="butto
 input[type="submit"],
 input[type="reset"],
 input[type="button"] {
-  &.btn-block {
-    width: 100%;
-  }
+  &.btn-block, &.Button--block { width: 100%; }
 }
 
 // Set the backgrounds
@@ -257,4 +260,20 @@ input[type="button"] {
     color: $textColor;
     background: transparent;
   }
+}
+
+
+// Handle jQueryUI-generated button classes
+.ui-button-icon-only .ui-button-text, .ui-button-icons-only .ui-button-text { @extend .ui-helper-hidden-accessible; }
+
+.ui-button {
+  position: relative;
+  @extend .Button;
+  &.ui-state-hover { @extend .Button:hover }
+  &.ui-state-focus { @extend .Button:focus }
+  &.ui-state-active { 
+    @extend .Button--active;
+    &:hover { @extend .Button--active; }
+  }
+  &.ui-state-disabled { @extend .Button.disabled; }
 }

app/stylesheets/vendor/bootstrap/_mixins.scss

@@ -579,12 +579,7 @@
       box-shadow: none;
     }
   }
-
-  &.disabled, &[disabled] {
-    cursor: not-allowed;
-    pointer-events: none;
-    opacity: 0.5;
-  }
+  
 }
 
 // Navbar vertical align

app/stylesheets/vendor/jqueryui/_jquery.ui.button.scss

@@ -1,5 +1,5 @@
 /*
-@styleguide Buttons: Button Set
+@styleguide Button Set
 
 We use jQuery UI button set
 
@@ -22,26 +22,6 @@ We use jQuery UI button set
 
 */
 
-.ui-button-icon-only .ui-button-text, .ui-button-icons-only .ui-button-text { @extend .ui-helper-hidden-accessible; }
-
-// DONT USE .ui-button, USE .btn INSTEAD!
-// it remains only because our jqueryUI widgets
-// (like 'dialog', and 'buttonset') generate .ui-buttons
-// in their markup.
-
-// make .ui-button mimic .btn styles
-.ui-button {
-  position: relative;
-  @extend .Button;
-  &.ui-state-hover { @extend .Button:hover }
-  &.ui-state-focus { @extend .Button:focus }
-  &.ui-state-active { 
-    @extend .Button--active;
-    &:hover { @extend .Button--active; }
-  }
-  &.ui-state-disabled { @extend .Button--active; }
-}
-
 .ui-buttonset {
   margin-right: 7px;
   .ui-button {