Made module handling much saner and safer

var/spack/mock_configs/site_spackconfig/compilers.yaml

@@ -6,12 +6,14 @@ compilers:
       f77: None
       fc: None
       modules: None
+      strategy: PATH
     gcc@4.5.0:
       cc: /path/to/gcc
       cxx: /path/to/g++
       f77: /path/to/gfortran
       fc: /path/to/gfortran
       modules: None
+      strategy: PATH
     gcc@5.2.0:
       cc: cc
       cxx: CC
@@ -20,6 +22,7 @@ compilers:
       modules:
         - PrgEnv-gnu
         - gcc/5.2.0
+      strategy: MODULES
     intel@15.0.1:
       cc: cc
       ccx: CC
@@ -28,8 +31,10 @@ compilers:
       modules:
       - PrgEnv-intel
       - intel/15.0.1
+      strategy: MODULES
     intel@15.1.2:
       cc: /path/to/icc
       cxx: /path/to/ic++
       f77: /path/to/ifort
       fc: /path/to/ifort
+      strategy: PATH