(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/LeftAlign.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 / LeftAlign</title>
+    <desc>Created with Sketch.</desc>
+    <g id="Icons-/-UI-/-LeftAlign" stroke="none" stroke-width="1" fill="none" fill-rule="evenodd">
+        <path d="M2.5,8.5 C2.22385763,8.5 2,8.27614237 2,8 C2,7.72385763 2.22385763,7.5 2.5,7.5 L13.5,7.5 C13.7761424,7.5 14,7.72385763 14,8 C14,8.27614237 13.7761424,8.5 13.5,8.5 L2.5,8.5 Z M2.5,4 C2.22385763,4 2,3.77614237 2,3.5 C2,3.22385763 2.22385763,3 2.5,3 L13.5,3 C13.7761424,3 14,3.22385763 14,3.5 C14,3.77614237 13.7761424,4 13.5,4 L2.5,4 Z M2.5,13 C2.22385763,13 2,12.7761424 2,12.5 C2,12.2238576 2.22385763,12 2.5,12 L7.5,12 C7.77614237,12 8,12.2238576 8,12.5 C8,12.7761424 7.77614237,13 7.5,13 L2.5,13 Z" id="Combined-Shape" fill="#000000" fill-rule="nonzero"></path>
+    </g>
+</svg>