Fixes #225 - Use a properly defined user agent

* Set a proper user agent
* Add fallback when UA comes out nil
* Remove unused Bundle extension
* Return nil when asciification fails
* Add whitespace handling and further emoji test case
* Explicitly check if string is already in ASCII
* Rename factory to builder
* Use allSatisfy instead of reduce
* Use key path syntax

IntegrationTests/SupportingFiles/target.yml

@@ -9,6 +9,8 @@ targets:
     - target: ElementX
     - package: MatrixRustSDK
       linkType: static
+    - package: DeviceKit
+      linkType: static
     - package: DTCoreText
       linkType: static
     - package: KeychainAccess