(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

static/ui-icons/Charts/ChartArea.svg

@@ -0,0 +1,9 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<svg width="16px" height="16px" viewBox="0 0 16 16" version="1.1" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink">
+    <!-- Generator: Sketch 52.5 (67469) - http://www.bohemiancoding.com/sketch -->
+    <title>Icons / Charts / ChartArea</title>
+    <desc>Created with Sketch.</desc>
+    <g id="Icons-/-Charts-/-ChartArea" stroke="none" stroke-width="1" fill="none" fill-rule="evenodd">
+        <path d="M3.19098301,8 L5.0527864,4.2763932 C5.18728544,4.00739512 5.52711181,3.91714933 5.7773501,4.08397485 L11.3316454,7.78683837 L15.0658784,1.25193053 C15.2028834,1.01217181 15.5083107,0.928873444 15.7480695,1.06587843 C15.9878282,1.20288341 16.0711266,1.50831075 15.9341216,1.74806947 L11.9341216,8.74806947 C11.7903974,8.99958678 11.4636827,9.07671366 11.2226499,8.91602515 L5.69391579,5.23020241 L4.13828424,8.34146551 L10.4459513,12.846942 L15.1464466,8.14644661 C15.461429,7.83146418 16,8.05454757 16,8.5 L16,15.0001095 C16,15.2762533 15.7761401,15.5001115 15.4999963,15.5001095 L0.499996349,15.5 C0.2238554,15.499998 0,15.2761409 0,15 L0,8.5 C0,8.22385763 0.223857625,8 0.5,8 L3.19098301,8 Z" id="Combined-Shape" fill="#000000" fill-rule="nonzero"></path>
+    </g>
+</svg>