[FIXED JENKINS-21060] Improve help text of "Number of successful release builds to keep"

Signed-off-by: Anders Hammar <anders@hammar.net>
[FIXED JENKINS-20983] Improve help text for "Preselect append Jenkins username" option

Signed-off-by: Anders Hammar <anders@hammar.net>
Fixed a few UI text items in the project configuration dialog to align with text items in release dialog.

Signed-off-by: Anders Hammar <anders@hammar.net>
[maven-release-plugin] prepare release m2release-0.13.0

Change-Id: I7c45d9201ed93a56ff40556a91ed28e6b9d9c88d