Cleanup from-source installation instructions
Cleanup from-source installation instructions

We were previously recommending setting both CMAKE_INSTALL_PREFIX and DESTDIR to
/opt/kudu, which would result in artifacts being installed into
/opt/kudu/opt/kudu. Additionally, we listed the installation step as optional,
but included it in the overall build script which skips optional steps.

Change-Id: Ib8d7d5e564d5b03a6f3bd092d8e1f2ad1aa17405
Reviewed-on: http://gerrit.cloudera.org:8080/1872
Reviewed-by: Misty Stanley-Jones <b9f9ef9e00c258208ea831c64cc129eda4ac78b4@apache.org>
Tested-by: Dan Burkert <2591e5f46f28d303f9dc027d475a5c60d8dea17a@cloudera.com>

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