Remove the javaVersionWithoutInitialOne hack/property that was introduced to allow specifying java versions as either 1.8 or 8:

It's not used in too many places: see the super-pom, and going forward I'd like the compiler plugin to use the javaVersion straight, which would mean a few things:

• force all 6.2 modules to change <javaVersion>1.8</javaVersion> to <javaVersion>8</javaVersion>, breaking change
• review other usages of javaVersion to ensure they accept 8, or turn the situation around: add the 1.${javaVersion} specifically in the compiler-jdk8 profile.
  • if building with JDK8, we can't build for newer versions anyway. But do we want to escape the chances of it resolving to 1.1.8 to not make it a breaking change then?
• javadoc plugin might need an update actually, to also use the <release> property instead of source accordingly.
• We could use the require property rule of the Maven enforce plugin to enforce the accepted format of Java version numbers.