NO-JIRA: Fix bug in doc generation for in-tree builds.

If cmake was run in the source tree, the doc generator would delete some doc source files.
Fixed this and removed the un-necessary site directory that was causing cmake warnings.

git-svn-id: https://svn.apache.org/repos/asf/qpid/dispatch/branches/0.4@1669618 13f79535-47bb-0310-9956-ffa450edef68
4 files changed