Add a cached property for the last_tagged_revision.  Provide get_changelog() method for Mercurial.
Add AUTO option to rez_install_cmake macro.

AUTO option allows rez_install_cmake to try to automatically set
common directories and discover libraries within the library_dirs.

NOTE: To achieve this, rez_install_cmake now executes after
installation.  The resulting cmake file is written directly
to the packages/release directory, and is no longer written
to the build directory.
Improve rez_install_cmake's report to the user.
Set static libraries to variables in rez_install_cmake macro.

Also add the CUSTOM_STRING argument, allowing the user to pass in
additional data to be written to the cmake file.  Libs in
<package>_LIBRARIES are now library names only - not full paths.