[UIMA-6463] Use toolchains to ensure compatibility with Java 1.8

[reckart]

JIRA Ticket: https://issues.apache.org/jira/browse/UIMA-6463

What's in the PR

• Add toolchain plugin

How to test manually

• No specific test procedure

Automatic testing

• [ ] PR adds/updates unit tests

Documentation

• [ ] PR adds/updates documentation

Organizational

• [ ] PR includes new dependencies. _{^{Only dependencies under approved licenses are allowed. LICENSE and NOTICE files in the respective modules where dependencies have been added as well as in the project root have been updated.}}