Option in QOptionGroup could be disabled (quasarframework#1082)

* More spacing classes

* Update size.styl

* Update size.styl

* Disabling options

* Update QOptionGroup.vue

Author: Iworb

src/components/option-group/QOptionGroup.vue

@@ -5,7 +5,7 @@
         :is="component"
         v-model="model"
         :val="opt.value"
-        :disable="disable"
+        :disable="disable || opt.disable"
         :label="opt.label"
         :left-label="leftLabel"
         :color="opt.color || color"