Guava is on the classpath twice, with different versions

While looking through the dependencies of yangide for an idea I had, I just noticed that Guava is twice on the classpath of yangide.yangparser, with different versions.. one a v15 from Orbit through MANIFEST, and one a v18 in lib as Bundle-Classpath.

This is typically Not Good, because which one gets loaded depends on classpath ordering, and this can be very confusing for developers when debugging.

We can probably safely simply remove either or the other. I'm assuming that the v18 in lib as Bundle-Classpath comes in for & via yangtools, so it seems smarter to keep that one and strike the other one.