Switching Git default branch to main

[Colm O hEigeartaigh <co...@apache.org>]

Hi all,

Unless I hear some strong objections I intend to file a JIRA with
INFRA to switch the default branch of the java git project from
"master" to "main". For some time any new GitHub project uses "main"
as the default branch, and most of the Apache projects I work with
(ActiveMQ, CXF, Karaf, Camel, etc.) have already made the change.

Once the change is made the easiest way is just to delete the local
copy and clone the repo again, or else there are some steps you can
follow to update the branch locally.

Colm.