Enabling Software Collections support

Fedora, RHEL, and CentOS have support for parallel installations of versions of software components such as python, perl, mariadb, etc.  One of the common ways to enable the use of a particular collection is to execute a bash shell from the invocation line.  That invocation looks like: 

    scl enable python27 mariadb55 bash

The software collection then sets an environment variable that is a white space separated list of all enabled collections

    X_SCLS=python27

An example of an enabled software collection in a python virtualenv in a git repo:

    [nzwulfin:~/oso/srtracker] [python27 mariadb55] [flask] master(+4/-1)* ± 

The [software collections website ](https://www.softwarecollections.org/en/) has more information about the implementation of the software.