app-text/languagetool: Bump guava SLOT, use Gentoo Java scripts

app-text/languagetool: Bump guava SLOT, use Gentoo Java scripts

guava:20 is needed so that Java 7 can be dropped from Gentoo.

Using our Java scripts makes the ebuild cleaner, avoids symlinks, and
ensures that the correct JVM is chosen at runtime.

There are still many external libraries being bundled and we don't
have the time to package them all right now but I have bumped jackson
and friends to a newer version than is bundled here so that can be
used and I've also introduced commons-collections:4.

I noticed that jna:0 was used before, which is version 3, but it's
actually version 4 that's bundled so I've amended that dependency.

This was given the +1 by Radhermit.

Package-Manager: portage-2.3.2