Multi-profile support; closes nima/site#28

It is now possible to have and switch between multiple profiles;
SITE_PROFILE is no longer used, instead a user utility (bin/activate)
has been introduced which allows you to create and switch between
various profiles.

In addition to this, the profile area has been moved out of the
site-specific VCS space and into `~/.site/profiles.d/'.

General house-keeping in `libsite.sh'.
Fixed `module/net'
Updated `module/vault': fix, enhanced
Updated `tests/remote'

Gracefully handle remote:copy failures for now (for whatever reason,
the test amended fails intermittently on Travic-CI).
... lib/libsh/libsite/libsite.sh