Feat/model backed ui (#1145)

This is an initial PR for a new model-driven UI where extensions can provide definitions of the components & how they're laid out using Containers.
#1140, #1141, #1142, #1143 and #1144 are all tracking additional work needed to improve the initial implementation and fix some issues with the implementation.

Features:
- Supports defining a FlexContainer that maps to a flexbox-based layout.
- Supports creating a card component, which is a key-value pair based control that will lay out simple information to a user. Eventually this will have an optional set of actions associated with it.
- Has a sample project which shows how to use the API and was used for verification

samples/sqlservices/sql/query.sql

@@ -0,0 +1,9 @@
+
+/*
+ * This file should contain SQL code that returns a result set
+ * To get started, build your own queries in SQL Operations Studio and click the
+ * "View as Chart" button to get the correct chart format. Then choose "Create Insight"
+ * and update the package.json with the JSON contents, and this file with the query
+ * used to generate the chart.
+ */
+select 'My Label' as [Label], 1 as [Value]