[Fixed Position] Allow straight lines

Pad width/height to give enough space to draw straight
lines; fix usage of background for boxes. WTD-880.

platform/features/layout/res/templates/elements/box.html

@@ -1,3 +1,3 @@
-<div ng-style="{ background: ngModel.fill }"
+<div ng-style="{ background: ngModel.element.fill }"
      style="width: 100%; height: 100%;">
 </div>

platform/features/layout/res/templates/elements/line.html

@@ -1,9 +1,9 @@
 <svg ng-attr-width="{{parameters.gridSize[0] * ngModel.width()}}"
      ng-attr-height="{{parameters.gridSize[1] * ngModel.height()}}">
-    <line ng-attr-x1="{{parameters.gridSize[0] * ngModel.x1()}}"
-          ng-attr-y1="{{parameters.gridSize[1] * ngModel.y1()}}"
-          ng-attr-x2="{{parameters.gridSize[0] * ngModel.x2()}}"
-          ng-attr-y2="{{parameters.gridSize[1] * ngModel.y2()}}"
+    <line ng-attr-x1="{{parameters.gridSize[0] * ngModel.x1() + 1}}"
+          ng-attr-y1="{{parameters.gridSize[1] * ngModel.y1() + 1}}"
+          ng-attr-x2="{{parameters.gridSize[0] * ngModel.x2() + 1}}"
+          ng-attr-y2="{{parameters.gridSize[1] * ngModel.y2() + 1}}"
           stroke="lightgray"
           stroke-width="2">
     </line>