Add 'pom.xml.versionsBackup'

'mvn versions:use-latest-versions' generates 'pom.xml.versionsBackup' file, because '-DgenerateBackupPoms=true' is default; see http://mojo.codehaus.org/versions-maven-plugin/use-latest-versions-mojo.html#generateBackupPoms
Merge pull request #1019 from nnuhanovic/patch-1

Add 'pom.xml.versionsBackup' to Maven template