Add lvm2 static compilation to Dockerfile

This is ported from the existing "dm" branch and cleaned up to be more idiomatic for the way Dockerfiles work (ie, if we change the lvm2 version, it'll rebuild from the correct line, and redo the "git clone" like it has to for us to have the tag), and also modified to only build the device-mapper code from lvm2 instead of building all the code and only installing device-mapper.  Finally, we're now installing the lvm2 source in "/usr/local/lvm2" to mirror/match our "/usr/local/go" installation (because consistency is king, hence the whitespace consistency commit here, too).

This also closes dotcloud/docker#2516 (by replacing it with a much better/cleaner solution).