improve python caching (#468)

(@dignifiedquire and @hpk42) 
- introduce rust-caching to python test runs 
- skip release and ffi runs, they are check using python bindings
- shuffle files such that ci_scripts/ contains all the ci scripts
- partly parallelize python tox runs

python/tests/test_increation.py

@@ -4,7 +4,7 @@ from deltachat import const
 from conftest import wait_configuration_progress, wait_msgs_changed
 
 
-class TestInCreation:
+class TestOnlineInCreation:
     def test_forward_increation(self, acfactory, data, lp):
         ac1 = acfactory.get_online_configuring_account()
         ac2 = acfactory.get_online_configuring_account()

python/tox.ini

@@ -19,12 +19,12 @@ deps =
     pytest-rerunfailures
     pytest-timeout
     pytest-xdist
-    auditwheel
     pdbpp
     requests
 
 [testenv:auditwheels]
 skipsdist = True
+deps = auditwheel
 commands = 
     python tests/auditwheels.py {toxworkdir}/wheelhouse
 
@@ -45,7 +45,7 @@ commands =
 [testenv:doc]
 basepython = python3.5
 deps =
-    sphinx==2.0.1
+    sphinx==2.2.0
     breathe
 
 changedir = doc