add ARCHITECURE file

ARCHITECTURE.md

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+### System architecture
+
+All the code is in the crowdsourcer app.
+
+Currently the app is structured round the way the CEUK Scorecards
+process works.
+
+In general there is one view for each stage of the process
+   * first mark
+   * right of reply
+   * audit
+
+plus one for the stats modules and a base view for code that is common
+across views.
+
+In general there is a base view for each page and then a class that
+extends that for each response stage.
+
+For each stage there is a page with a User's assignments grouped by
+section, one for the specific councils within that section and then a
+question page.
+
+A user can answer the same question multiple times and it will update
+the data. Previous responses are stored using HistoricalRecords from the
+simple_history package which creates a `crowdsourcer_historicalresponse`
+table.
+
+Superusers have access to view all stages at all times as well as access
+to the stats menu which provides various summary data.
+
+The important models are:
+
+ * PublicAuthority - local authority details
+ * Section - question sections
+ * Question - Question details
+ * Option - Possible answers for a Question
+ * Response - Answer for a question
+ * Assigned - Volunteer assignments
+ * Marker - Extra information about a user