Make concept based table IDs 64 bit

While we still have some headroom for the datasets we work with at the
moment, keeping the IDs of concept table based tables (inheritance) at
32 bit would have been a limit at some point. Already we see large
segmentation datasets that make this headroom rather small. Therefore
this migration will rewrite all concept based tables as well as tables
that reference them through foreign keys so that 64 bit IDs are used.

This migration also updates the review table to use 64 bit IDs. It also
fixes the history views of the catmaid_sampler table, which haven't been
kept up to date with column changes.

In addition a lot of missing foreign key constraints have been added.
They shouldn't have a big import on performance and in fact no real
difference could be measured.

The column order of concept changed slightly to improve the column
alignment and reduce padding. So far we wasted 4 Bytes per row, because
project_id occupied 4 Bytes and required 4 Bytes of padding, because it
was followed by a bigint. This is changed now and no more padding is
needed. This also lowers the impact on storage of the change to 64 bit
IDs.

Fixes #1848

CHANGELOG.md

@@ -40,6 +40,9 @@ Contributors: Chris Barnes, Albert Cardona, Andrew Champion, Stephan Gerhard, Pa
   Postgres superuser:
   `sudo -u postgres psql -d <catmaid-db> -c 'CREATE EXTENSION pg_trgm;'`
 
+- Due to changes in the database schema, migration 70 might take a while to
+  complete.
+
 - CATMAID's version information changes back to a plain `git describe` format.
   This results overall in a simpler setup and makes live easier for some
   third-party front-ends, because the commit counter is included again. The

django/applications/catmaid/migrations/0071_fix_change_request_ids.py

@@ -0,0 +1,44 @@
+# Generated by Django 2.1.8 on 2019-05-29 12:46
+
+from django.db import migrations
+
+
+forward = """
+    UPDATE change_request
+    SET id = nextval('concept_id_seq');
+
+    ALTER TABLE ONLY change_request ALTER COLUMN id SET DEFAULT nextval('concept_id_seq'::regclass);
+
+    DROP SEQUENCE change_request_id_seq;
+"""
+
+backward = """
+    CREATE SEQUENCE change_request_id_seq
+        START WITH 1
+        INCREMENT BY 1
+        NO MINVALUE
+        NO MAXVALUE
+        CACHE 1;
+
+    ALTER SEQUENCE change_request_id_seq OWNED BY change_request.id;
+
+    ALTER TABLE ONLY change_request ALTER COLUMN id SET DEFAULT nextval('change_request_id_seq'::regclass);
+
+    UPDATE change_request
+    SET id = nextval('concept_id_seq');
+"""
+
+class Migration(migrations.Migration):
+    """This removes the ID sequence the change_requests table is using and makes
+    it use the regular concept ID sequence (it inherits from concept). New IDs
+    will be assigned to all change requests. It is not possible to revert to the
+    original IDs.
+    """
+
+    dependencies = [
+        ('catmaid', '0070_remove_pg10_bug_workaround'),
+    ]
+
+    operations = [
+        migrations.RunSQL(forward, backward)
+    ]