rn: set version to 19.0.0

This marks our switch to CalVer: http://calver.org/

Major: year
Minor: release number
Patch: build (in case we need to retry)

android/gradle.properties

 # http://www.gradle.org/docs/current/userguide/multi_project_builds.html#sec:decoupled_projects
 # org.gradle.parallel=true
 
-buildNumber=2
-appVersion=1.21.0
+buildNumber=1
+appVersion=19.0.0
 sdkVersion=1.21.0

ios/app/src/Info.plist

 	<key>CFBundlePackageType</key>
 	<string>APPL</string>
 	<key>CFBundleShortVersionString</key>
-	<string>1.21</string>
+	<string>19.0.0</string>
 	<key>CFBundleSignature</key>
 	<string>????</string>
 	<key>CFBundleURLTypes</key>