Use chessboard squares (vs interior corners); fix resolution selector bug (#139)

* Change chessboard size to be squares not interior corners

This reduces ambiguity

* Force users to select resolution

This forces the correct video mode index to be selected. Otherwise the 0th camera videomode index will be used, as it's zero-inited. This is undesirable.

* Make target model an enum

This will allow the UI to remember the currently selected target.

photon-client/src/store/index.js

@@ -122,8 +122,8 @@ export default new Vuex.Store({
             minCount: 25,
             hasEnough: false,
             squareSizeIn: 1.0,
-            patternWidth: 7,
-            patternHeight: 7,
+            patternWidth: 8,
+            patternHeight: 8,
             boardType: 0, // Chessboard, dotboard
         },
         metrics: {