[doc] Rename starter projects on download page

[wsargent]

Play Version (2.5.x / etc)

2.5.x

API (Scala / Java / Neither / Both)

Neither

Actual Behavior

See https://playframework.com/download -- the example project service lists "Play Example "rpoject

The example code service renders play-java and play-scala as "Play Java Seed" and "Play Scala Seed", which is not accurate -- they're more like very simple example projects, i.e. they show off functionality you have to remove later. We should define the giter8 projects as the official seeds, and rename these projects from the example-code-service json store.