Fix relocation of Guava libraries

The Guava library is not relocated into org.bukkit.craftbukkit.libs as expected, instead it included at the top-level where it may conflict with other copies of Guava. This PR updates the relocation patterns to include Guava under org.bukkit.craftbukkit.libs.com.google in the shaded jar, where all the other (relocateable) libraries are included.

Leaky ticket forthcoming