Organize test-cases into folders, extract compatibility test into proper test, support adding test-case specific tests

betterproto/tests/inputs/bool/bool.json

@@ -0,0 +1,3 @@
+{
+  "value": true
+}

betterproto/tests/inputs/bool/bool.proto

@@ -0,0 +1,5 @@
+syntax = "proto3";
+
+message Test {
+    bool value = 1;
+}

betterproto/tests/inputs/bool/test.py

@@ -0,0 +1,8 @@
+from betterproto.tests.output_betterproto.bool.bool import Test
+from betterproto.tests.util import read_relative
+
+
+def test_value():
+    message = Test().from_json(read_relative(__file__, 'bool.json'))
+    assert message.value
+