Add external import sources, work history, screening fields and Phase 1 docs

- New ExternalImportSource and ExternalWorkHistoryEntry models, controller and migrations
- Screening fields on external profile imports
- Admin and provider profile views, routes and workflow tests updated
- Phase 1 validation, route inventory, gap report template and roadmap docs
- Add the Google Sheets work-order parser tool (tools/google-sheets-wo-parser)

tools/google-sheets-wo-parser/appsscript.json

@@ -0,0 +1,11 @@
+{
+  "timeZone": "America/Chicago",
+  "exceptionLogging": "STACKDRIVER",
+  "runtimeVersion": "V8",
+  "oauthScopes": [
+    "https://www.googleapis.com/auth/spreadsheets",
+    "https://mail.google.com/",
+    "https://www.googleapis.com/auth/script.scriptapp"
+  ]
+}
+