task/install.py: Allow installation of non-ceph

task/install.py: Allow installation of non-ceph

Generalizes the install task to specify a "project" which defaults to
'ceph', but can be configured to install different project packages,
for example:

install:
  project: samba
  extra_packages: samba

The default install task uses 'ceph' as the project, and relies on an
existing set of defined packages to install.  For other projects, the
packages to be installed must be specified with the extra_packages
field.  Multiple install tasks can be specified:

install:
install:
  project: samba
  extra_packages: samba

Which installs ceph packages and then samba packages.

Also, cleanup in nuke.py so that nuke and install use the same list of
packages when doing the remove steps.

Signed-off-by: Sam Lang <sam.lang@inktank.com>