Flexbox ios initial commit

Items now appear, but they should initially shrink and they don't

Add 15-ish tests for flexbox layout

Port reasonable flexbox test set

Fixing issues, adding unit tests

Moved from .tsx to .ts and used our ui/builder.parse

tsconfig.json

@@ -10,6 +10,8 @@
         "experimentalDecorators": true,
         "diagnostics": true,
         "sourceMap": true,
+        "jsx": "react",
+        "reactNamespace": "UIBuilder",
         "lib": [
             "es2016"
         ]