Backport statistics app, remove statistic code from the main app, convert the documents and ocr apps to use the new statictics app code

mayan/apps/statistics/classes.py

@@ -0,0 +1,58 @@
+class StatisticNamespace(object):
+    _registry = {}
+
+    @classmethod
+    def get_all(cls):
+        return cls._registry.values()
+
+    @classmethod
+    def get(cls, name):
+        return cls._registry[name]
+
+    def __init__(self, name, label):
+        self.name = name
+        self.label = label
+        self._statistics = []
+        self.__class__._registry[name] = self
+
+    def __unicode__(self):
+        return unicode(self.label)
+
+    def add_statistic(self, statistic):
+        self._statistics.append(statistic)
+        statistic.namespace = self
+
+    @property
+    def id(self):
+        return self.name
+
+    @property
+    def statistics(self):
+        return self._statistics
+
+
+class Statistic(object):
+    _registry = {}
+
+    @classmethod
+    def get_all(cls):
+        return cls._registry.values()
+
+    @classmethod
+    def get(cls, name):
+        return cls._registry[name]
+
+    def __init__(self, name, label):
+        self.name = name
+        self.label = label
+        self.__class__._registry[name] = self
+
+    def __unicode__(self):
+        return unicode(self.label)
+
+    def get_results(self, *args, **kwargs):
+        return NotImplemented
+
+    @property
+    def id(self):
+        return self.name