Introduce default assignment simplifications

There are many simplifications in pystencils that are usually not applied. They can be applied now by using a simple argument in the configuration.

Fixes #39 (closed)

.gitlab-ci.yml

@@ -239,7 +239,7 @@ pycodegen-integration:
   allow_failure: true
   script:
     - source /opt/conda/etc/profile.d/conda.sh
-    - source activate pystencils_dev
+    - conda activate pystencils_dev
     - git clone https://gitlab-ci-token:${CI_JOB_TOKEN}@i10git.cs.fau.de/pycodegen/pycodegen.git
     - cd pycodegen
     - git submodule sync --recursive