feat: bring back and adapt python bindings with rust core

* import python, try to adapt for rust

* add missing wrapper functions

* - try to write up how to build python bindings
- strike some unused functions from deltachat.h

* adjustments to make tox work

* try to run circle-ci with python build

* don't do docs

* running cargo test as well

* don't run cargo test anymore, that's done in other ci jobs

* also build docs

* don't run doxygen anymore

* subst C with Rust

* a try to get better wheels

Closes #41

python/tests/test_lowlevel.py

@@ -0,0 +1,29 @@
+from __future__ import print_function
+import pytest
+from deltachat import capi, Account, const
+
+
+def test_empty_context():
+    ctx = capi.lib.dc_context_new(capi.ffi.NULL, capi.ffi.NULL, capi.ffi.NULL)
+    capi.lib.dc_close(ctx)
+
+
+def test_wrong_db(tmpdir):
+    tmpdir.join("hello.db").write("123")
+    with pytest.raises(ValueError):
+        Account(db_path=tmpdir.strpath)
+
+
+def test_event_defines():
+    assert const.DC_EVENT_INFO == 100
+    assert const.DC_CONTACT_ID_SELF
+
+
+def test_sig():
+    sig = capi.lib.dc_get_event_signature_types
+    assert sig(const.DC_EVENT_INFO) == 2
+    assert sig(const.DC_EVENT_WARNING) == 2
+    assert sig(const.DC_EVENT_ERROR) == 2
+    assert sig(const.DC_EVENT_SMTP_CONNECTED) == 2
+    assert sig(const.DC_EVENT_IMAP_CONNECTED) == 2
+    assert sig(const.DC_EVENT_SMTP_MESSAGE_SENT) == 2