core library (#711)

* move app creation to function

* create engine without load

* flake 8 fixes

* cleanup original scanpy test

* add default config

* handle missing data

* test data changes

* unify update

* load data isn't static anymore

* make app a class

server/app/util/errors.py

@@ -50,3 +50,12 @@ class ScanpyFileError(Exception):
 
     def __init__(self, message):
         self.message = message
+
+
+class DriverError(Exception):
+    """
+    Raised when file loaded into scanpy is misformatted
+    """
+
+    def __init__(self, message):
+        self.message = message