(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/UI/Wrap.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 / UI / Wrap</title>
+    <desc>Created with Sketch.</desc>
+    <g id="Icons-/-UI-/-Wrap" stroke="none" stroke-width="1" fill="none" fill-rule="evenodd">
+        <path d="M9,12 L9,13 L8.30782366,11.9617355 C8.12706483,11.8864148 8,11.7080462 8,11.5 C8,11.2919538 8.12706483,11.1135852 8.30782274,11.0382659 L9,10 L9,11 L11.326087,11 C12.2466415,11 13,10.2202739 13,9.25 C13,8.27972605 12.2466415,7.5 11.326087,7.5 L2.5,7.5 C2.22385763,7.5 2,7.27614237 2,7 C2,6.72385763 2.22385763,6.5 2.5,6.5 L11.326087,6.5 C12.8067705,6.5 14,7.73499257 14,9.25 C14,10.7650074 12.8067705,12 11.326087,12 L9,12 Z M2.5,2 L13.5,2 C13.7761424,2 14,2.22385763 14,2.5 C14,2.77614237 13.7761424,3 13.5,3 L2.5,3 C2.22385763,3 2,2.77614237 2,2.5 C2,2.22385763 2.22385763,2 2.5,2 Z M2.5,11 L5.5,11 C5.77614237,11 6,11.2238576 6,11.5 C6,11.7761424 5.77614237,12 5.5,12 L2.5,12 C2.22385763,12 2,11.7761424 2,11.5 C2,11.2238576 2.22385763,11 2.5,11 Z" id="Combined-Shape" fill="#000000" fill-rule="nonzero"></path>
+    </g>
+</svg>