Overhauled `module/xplm'

The installer no longer handles XPLM virtual environments, as this is
an optional feature offered by site, and slows the installer
significantly.  The XPLM modules handles this itself now.

The `xplm.conf' file has been removed.

New functions to more closely interact with the various virtualenv
frameworks.

General cleanup.
Unit test `xplm' added: nima/site#34
Updated `README.md': added rb, py, pl, and xplm

The `.travis.yml' has been updated to know about (but ignore failure
of (for now)) the new modules, since unit-testing is incomplete.
Updated `module/ldap': retrospective updates

Much has changed since this module was last tested, and this commit
get this module re-aligned with what is current.
Updated `module/ng': retrospective updates

Much has changed since this module was last tested, and this commit
get this module re-aligned with what is current.
Updated `module/mongo'