[m2e-dev] m2e master branch requires java 8

[Igor Fedorenko <igor@xxxxxxxxxxxxxx>]

FYI, I've updated m2e master branch to version 1.7.0-SNAPSHOT and
changed bundle manifests to require java 8. The build works and all
tests pass in our linux CI system [1] and on my macbook (you need to
trust me on this), but let me know if you see anything unexpected. 

We should mention java 8 requirement on crosspatform-dev if we decide to
contribute m2e 1.7 to the next year simultaneous release, but I don't
think anyone volunteered to do the work yet.

[1] https://ci.takari.io/

-- 
Regards,
Igor