This patch adds a new function QueryAllChanges to gerrit_util.py
allowing the caller to iterate the list of changes regardless the
maximum limit of changes per request that the server supports (by
default 500 according to gerrit's documentation).

my_activity.py is ported to use this function instead of urllib2 to
manually make the request. This also adds support for authentication
since gerrit_util.py already supports it, and the internal gerrit
instance is now re-enabled.

Finally, two minor bugs are fixed on the hanlding of returned
results: The DETAILED_ACCOUNTS option is passed to gerrit to request
the email addresses of the referenced users and users without an
email address, such as the "Gerrit Code Review" user on the internal
gerrit, are now supported.

BUG=chromium:311649,chromium:281695
TEST=Manual run "my_activity.py -u USER" for some users.

Review URL: https://codereview.chromium.org/50283002

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@233166 0039d316-1c4b-4281-b951-d872f2087c98