Reorganize RPM package directories and support chaning to a non-root user.
- Renamed and moved src/opentsdb-init-d.sh to build-aux/init.d/opentsdb.
- Made the RPM directory structure similar to that of the Debian package.
- Copied build-aux/deb/opentsdb.conf to build-aux/rpm/opentsdb.conf.
- Copied jars to /usr/share/opentsdb/lib during installation.
- Left a TODO for the alternatives.
- Changed the owner of files touched by OpenTSDB.
*** For the existing OpenTSDB installations, we should modify the init script
symbolic links to point to the new target.

New directory structure:
-----------
rpmbuildroot/usr/share/opentsdb:
  bin/  etc/  lib/  static/  tools/
rpmbuildroot/usr/share/opentsdb/etc:
  init.d/  opentsdb/
rpmbuildroot/var/cache:
  opentsdb/