Changed the names of files and modules to make them consistent with the class names

examples/run_examples.sh

@@ -2,7 +2,7 @@
 
 for i in $(ls example_*.py); do
     echo "=== Execute $i ==="
-    python3 "$i"
+    python "$i"
     if [ $? != 0 ]; then
         break
     fi

svirl/__init__.py

@@ -8,7 +8,7 @@ from svirl import config as cfg
 
 from svirl import parallel  as GLPar 
 from svirl import mesh      as GLMesh
-from svirl import variables as GLVars
+from svirl import vars      as GLVars
 from svirl import observables as GLObs
 from svirl import solvers as GLSolvers
 

svirl/vars/__init__.py

@@ -2,5 +2,5 @@
 # Licensed under the MIT license.
 
 from .fixed_vortices import FixedVortices 
-from .variables import Vars
-from .parameters import Params
+from .vars import Vars
+from .params import Params