improve app startup time

[mpoehler]

There are some things that can be done to speed up app startup, follow these Tips here

But first, check out how app startup time can be measured in the production system and then check all points from the source above and others.

[mpoehler]

consider: https://cloud.google.com/appengine/docs/java/config/appconfig#Java_appengine_web_xml_Warmup_requests