Cleaned up deployment & install

- moved Dockerfiles into separate directory
- tests for minimal setup on ubuntu & conda
- adapted setup scripts to correctly handle dependencies
- new conda environment files for users and developers

__init__.py

+import pystencils.sympy_gmpy_bug_workaround
 from pystencils.field import Field, FieldType
 from pystencils.data_types import TypedSymbol
 from pystencils.slicing import make_slice

sympy_gmpy_bug_workaround.py

+# Disable gmpy backend until this bug is resolved if joblib serialize
+# See https://github.com/sympy/sympy/pull/13530
+import os
+import warnings
+
+os.environ['MPMATH_NOGMPY'] = '1'
+try:
+    import mpmath.libmp
+    # In case the user has imported sympy first, then pystencils
+    if mpmath.libmp.BACKEND == 'gmpy':
+        warnings.warn("You are using the gmpy backend. You might encounter an error 'argument is not an mpz sympy'."
+                      "This is due to a known bug in sympy/gmpy library. "
+                      "To prevent this, import pystencils first then sympy or set the environment variable "
+                      "MPMATH_NOGMPY=1")
+except ImportError:
+    pass