(core) move client code to core

Summary:
This moves all client code to core, and makes minimal fix-ups to
get grist and grist-core to compile correctly.  The client works
in core, but I'm leaving clean-up around the build and bundles to
follow-up.

Test Plan: existing tests pass; server-dev bundle looks sane

Reviewers: dsagal

Reviewed By: dsagal

Differential Revision: https://phab.getgrist.com/D2627

app/client/models/rowuid.js

@@ -0,0 +1,48 @@
+/**
+ * For some purposes, we need to identify rows uniquely across different tables, e.g. when showing
+ * data with subtotals. This module implements a simple and reasonably efficient way to combine a
+ * tableRef and rowId into a single numeric identifier.
+ */
+
+
+
+// A JS Number can represent integers exactly up to 53 bits. We use some of those bits to
+// represent tableRef (the rowId of the table in _grist_Tables meta table), and the rest to
+// represent rowId in the table. Note that we currently never reuse old ids, so these limits apply
+// to the count of all tables or all rows per table that ever existed, including deleted ones.
+const MAX_TABLES = Math.pow(2, 18);     // Up to ~262k tables.
+const MAX_ROWS = Math.pow(2, 35);       // Up to ~34 billion rows.
+exports.MAX_TABLES = MAX_TABLES;
+exports.MAX_ROWS = MAX_ROWS;
+
+/**
+ * Given tableRef and rowId, returns a Number combining them.
+ */
+function combine(tableRef, rowId) {
+  return tableRef * MAX_ROWS + rowId;
+}
+exports.combine = combine;
+
+/**
+ * Given a combined rowUid, returns the tableRef it represents.
+ */
+function tableRef(rowUid) {
+  return Math.floor(rowUid / MAX_ROWS);
+}
+exports.tableRef = tableRef;
+
+/**
+ * Given a combined rowUid, returns the rowId it represents.
+ */
+function rowId(rowUid) {
+  return rowUid % MAX_ROWS;
+}
+exports.rowId = rowId;
+
+/**
+ * Returns a human-readable string representation of the rowUid, as "tableRef:rowId".
+ */
+function toString(rowUid) {
+  return typeof rowUid === 'number' ? tableRef(rowUid) + ":" + rowId(rowUid) : rowUid;
+}
+exports.toString = toString;