Roll back Ivy to 2.3.0 for 0.13.5
Merge pull request #1357 from sbt/wip/roll-back-ivy

Roll back Ivy to 2.3.0 for 0.13.5 for #1356
0.13.5 release.
Fix import issues to generate sxr/scaladoc.
Merge remote-tracking branch 'origin/0.13.5' into wip/fix-doc-generation

Conflicts:
	project/Sbt.scala
Fix formatting issues and bump to sbt 0.13.5
Merge pull request #1376 from sbt/wip/fix-doc-generation

Merge 0.13.5 into 0.13