420848 - maven-compiler-plugin source/target 1.8 not recognized

The jdt component of m2e v1.4 does not import java 1.8 projects correctly into eclipse.
Instead of setting the compiler compliance level to java 1.8, java 1.4 is used.
This patch fixes this issue by adding JavaSE-1.8 to the list of known java runtime environments
and adding java 1.8 (respectively java 8) to the list of known source/target compliance levels.

This contribution complies with http://www.eclipse.org/legal/CoO.php

Bug: https://bugs.eclipse.org/bugs/show_bug.cgi?id=420848
Signed-off-by: Daniel Dietrich <daniel.dietrich@gmx.net>