Upgrade build to JDK 1.8 bytecode

[tumbarumba]

The JavaHamcrest build is currently running on an unsupported version of Gradle (4.10) against an unsupported build target (JRE 1.7 bytecode).

We should:

• Upgrade to the latest Gradle (version 8.8 as of this issue)
  • This will require we migrate to the bnd OSGI bundling plugin
• Change the bytecode target from 1.7 to 1.8

[tumbarumba]

I was a bit trigger happy in creating this new issue, as there are already existing issues (see #206, #207, and #331). I'll work against those issues instead