Updated build system to Free Desktop Standard

This PR aims to bring the cyclus build system more in-line with the [free desktop standard for base directories*](http://standards.freedesktop.org/basedir-spec/basedir-spec-latest.html) by adjusting the install directory.  

This basically states that user files that aren't configuration (everything here) should go into a `${HOME}/.local` directory whose structure mirrors that of root in the posix standard.  The current systems prepends a `cyclus/` dir to its input path which makes it impossible to adhere to the standard.  This pull request removes that `cyclus/`.

Note that this does not forbid users who want a separate `cyclus/` dir from having it.  They simply have to do this manually by giving the `-DCMAKE_INSTALL_PREFIX=${BASE_INSTALL_DIR}/cyclus/` option. when cmake is run.

* Note that this is used by a wide variety of other projects, such as Gnome, KDE, Chrome, Firefox, most window managers (including awesome), Python, etc.