(core) Barely working reference lists in frontend

Summary:
This makes it possible to set the type of a column to ReferenceList, but the UI is terrible

ReferenceList.ts is a mishmash of ChoiceList and Reference that sort of works but something about the CSS is clearly broken

ReferenceListEditor is just a text editor, you have to type in a JSON array of row IDs. Ignore the value that's present when you start editing. I can maybe try mashing together ReferenceEditor and ChoiceListEditor but it doesn't seem wise.
I think @georgegevoian should take over here. Reviewing the diff as it is to check for obvious issues is probably good but I don't think it's worth trying to land/merge anything.

Test Plan: none

Reviewers: dsagal

Reviewed By: dsagal

Subscribers: georgegevoian

Differential Revision: https://phab.getgrist.com/D2914

sandbox/grist/summary.py

@@ -121,11 +121,16 @@ class SummaryActions(object):
     """
     key = tuple(sorted(int(c) for c in source_groupby_columns))
 
-    groupby_colinfo = [_make_col_info(col=c,
-                                      isFormula=False,
-                                      formula='',
-                                      type='Choice' if c.type == 'ChoiceList' else c.type)
-                       for c in source_groupby_columns]
+    groupby_colinfo = [
+      _make_col_info(
+        col=c,
+        isFormula=False,
+        formula='',
+        type='Choice' if c.type == 'ChoiceList' else
+        c.type.replace('RefList:', 'Ref:')
+      )
+      for c in source_groupby_columns
+    ]
     summary_table = next((t for t in source_table.summaryTables if t.summaryKey == key), None)
     created = False
     if not summary_table: