Use tabs instead of spaces in pom.xml files

This is consistent with the use of tabs in the Java sources.
Fix up @author tags

Use real names, and remove email addresses. The formatting was
inconsistent, and the same email address was not always used for the
same author. The email addresses are recorded in the Git commits, as
well as in the Maven POMs, so putting them in the @author tags too is
both redundant and error-prone.
pom.xml: fix Mark's email address
.mailmap: fix duplicate jmoore author entry

I am talking about "git shortlog -nse" here, of course. With this
change, all of Josh's commits are grouped together, as desired.