Include xcmisc extension in core

Support generation of xcmisc extension, and include the extension in
core.
Generate xcmisc

Generate the xcmisc extension.
Add xcmisc to reply dispatcher
Update gitignore

Ignore logback-test.xml.
Add Hamcrest Matchers as test dependency

Add Hamcrest Matchers library as test dependency, which provides many
useful matchers.
Test for xcmisc

Add tests to exercise the xcmisc extension, and extension handling in
general.
Ask for more XIDs after it runs out

Ask for more XIDs using xcmisc after they run out.