As discussed in #32 and merged in #33, we need to explain / amplify the documentation surrounding --element_regex_global and the new functionality of --element. cc @Project0

This issue has happened previously (see infra issue #145) - /usr/bin/dockerd (deleted)
This is causing Docker-based tests to fail (see openjdk8_hs_externaltest_x86-64_linux/52)

Comment from previous infra issue:
"Apparently the error fork/exec /usr/bin/dockerd (deleted): no such file o