Omnidoc fails on JDK11

[ignasi35]

Running sbt +publish for omnidoc using JDK11 ends successfully, even though the output is incomplete and some internal steps actually fail.

See for example:

[warn] javadoc: error - No source files for package play
[warn] 1 error.
[warn] javadoc exited with exit code 2
[info] Omnidoc Java API documentation successful.

I know that at least the omnidoc/javadoc folder is empty. But I can't be sure about other expected outputs. There seems to be generated data in both omnidoc/scaladoc and omnidoc/playdoc but I didn't check if the output is complete.

[dwijnand]

This might've been fixed in sbt 1.3, so perhaps worth checking after upgrading.

[ignasi35]

This might've been fixed in sbt 1.3, so perhaps worth checking after upgrading.

LOL #71 and #103 🤦🏼‍♂️

[mkurz]

Fixed by #110, also Travis tests against Java 11 meanwhile and looks good.