Fix a couple bugs in make_site.sh
Fix a couple bugs in make_site.sh

This patch fixes a couple minor script bugs:

* zip command should not quote arguments
* doxygen output appears in build dir, not source dir

Also makes a couple other minor changes:

* Run doxygen by default so people updating the site don't tend to
  forget to run it, but retain an option to skip it
* Add a --help option to the command

Tested on Ubuntu 16.04 in both default and --no-doxygen modes, with and
without doxygen installed.

Change-Id: I3332fc36c9e33baed82f3eabfb5866a9cd41422f
Reviewed-on: http://gerrit.cloudera.org:8080/3780
Tested-by: Kudu Jenkins
Reviewed-by: Adar Dembo <866ca730bfc7f544e3ebce604ceeba4879f23df0@cloudera.com>

andrwng/kudu,andrwng/kudu,helifu/kudu,InspurUSA/kudu,cloudera/kudu,InspurUSA/kudu,helifu/kudu,helifu/kudu,helifu/kudu,InspurUSA/kudu,cloudera/kudu,andrwng/kudu,andrwng/kudu,andrwng/kudu,InspurUSA/kudu,EvilMcJerkface/kudu,andrwng/kudu,cloudera/kudu,helifu/kudu,andrwng/kudu,EvilMcJerkface/kudu,EvilMcJerkface/kudu,cloudera/kudu,cloudera/kudu,InspurUSA/kudu,InspurUSA/kudu,InspurUSA/kudu,EvilMcJerkface/kudu,EvilMcJerkface/kudu,cloudera/kudu,InspurUSA/kudu,cloudera/kudu,cloudera/kudu,EvilMcJerkface/kudu,helifu/kudu,helifu/kudu,andrwng/kudu,helifu/kudu,helifu/kudu,EvilMcJerkface/kudu,cloudera/kudu,andrwng/kudu,InspurUSA/kudu,EvilMcJerkface/kudu,EvilMcJerkface/kudu