(core) Expanding widgets

Summary:
New icon to expand an active section and show it as a popup (just like raw data views).

"Show raw data" popup couldn't be reused (as it is basically a different page), so now
we have two kinds of popups that look the same.

1. Raw data popup - to show an alien section on a page (a section from a different view). This is used by "Show raw data" button, it is basically a different page that shows an arbitrary section.

2. Layout popup - a popup generated by Layout.ts that basically hides every other section and adds an overlay effect to itself.

Other changes
- Layout.js was migrated to typescript
- "Show raw data" menu item was converted to link

Test Plan: new tests

Reviewers: georgegevoian

Reviewed By: georgegevoian

Differential Revision: https://phab.getgrist.com/D3764

app/client/ui2018/IconList.ts

@@ -67,6 +67,7 @@ export type IconName = "ChartArea" |
   "FontStrikethrough" |
   "FontUnderline" |
   "FunctionResult" |
+  "Grow" |
   "Help" |
   "Home" |
   "Idea" |
@@ -200,6 +201,7 @@ export const IconList: IconName[] = ["ChartArea",
   "FontStrikethrough",
   "FontUnderline",
   "FunctionResult",
+  "Grow",
   "Help",
   "Home",
   "Idea",