Refactoring form RPM build

Shells and Build Directory Structure to have a "better" structure
for an RPM build and usage in a production environment.

New shell that manages environment variables.
    * bin/mesos-profile-env.sh.in - Should be loaded through `/etc/profile.d`
    * bin/mesos-build-env.sh.in doesn't exist anymore, use
        `bin/mesos-profile-env.sh` is now expected to be preloaded.

Modified several shells to use `$MESOS_HOME` instead of hardcoading the
directory.

    * bin/gdb-mesos-local.sh.in
    * bin/gdb-mesos-master.sh.in
    * bin/gdb-mesos-slave.sh.in
    * bin/gdb-mesos-tests.sh.in
    * bin/mesos-master.sh.in
    * bin/mesos-tests.sh.in
    * bin/mesos-master.sh.in
    * bin/mesos-tests.sh.in

New Init Scripts
    * bin/init.d-mesos-locald
    * bin/init.d-mesos-masterd
    * bin/init.d-mesos-slaved

RPM SPEC
    * rpm/apache-mesos.spec

Other changes in bin shells worth mentioning.

    *   MESOS_WEBUI_DIR: `@abs_top_srcdir@/src/webui` changed to
        `$MESOS_HOME/lib/webui`
    *   MESOS_LAUNCHER_DIR: `@abs_top_builddir@/src` changed to
        `$MESOS_HOME/lib`
    *   MESOS_KILLTREE:   `@abs_top_srcdir@/src/scripts/killtree.sh` changed
        to `$MESOS_HOME/lib/scripts/killtree.sh`
    *   We now look for the `mesos-master` library at
    *   `$MESOS_HOME/lib/mesos-master` instead of
    *   `@abs_top_builddir@/src/mesos-master`
    *   Supporting scripts are located at `$MESOS_HOME/support`, e.g. the
    *   `colors.sh` script is now located at
    *   `$MESOS_HOME/support/colors.sh`.