Theme consistency overhaul:

- Add surface shift option, start from surface by default (previously
  was surfaceContainer). Old colors can be attained by changing it back
to "container" in theme colors
- Remove borders on surface elements, mostly
- Fix popup distances
- Use surfaceContainer/sch by default on widgets

Modules/ProcessList/SystemTab.qml

@@ -24,7 +24,7 @@ DankFlickable {
             width: parent.width
             height: systemInfoColumn.implicitHeight + 2 * Theme.spacingL
             radius: Theme.cornerRadius
-            color: Qt.rgba(Theme.surfaceContainer.r, Theme.surfaceContainer.g, Theme.surfaceContainer.b, 0.6)
+            color: Theme.surfaceContainerHigh
             border.width: 0
 
             Column {
@@ -386,7 +386,7 @@ DankFlickable {
             width: parent.width
             height: storageColumn.implicitHeight + 2 * Theme.spacingL
             radius: Theme.cornerRadius
-            color: Qt.rgba(Theme.surfaceContainer.r, Theme.surfaceContainer.g, Theme.surfaceContainer.b, 0.6)
+            color: Theme.surfaceContainerHigh
             border.width: 0
 
             Column {