Load setup files instead of sourcing them

- needed for same setup files to work on Windows
  (where PowerShell is used instead of bash)
- removes ugly bashism to allow overriding from .travis.yml
- adds a proper (yet small) syntax
Also adds tests for the new syntax and updates the README.

test01.set

@@ -1,4 +1,4 @@
 MODULES="sncseq"
 
-BASE=${BASE:-7.0}
-SNCSEQ=${SNCSEQ:-R2-2-7}
+BASE=7.0
+SNCSEQ=R2-2-7