Split common into composite subprojects with project references

- common/tsconfig.json is a solution root referencing layer tsconfigs
- Each layer has composite tsconfig with correct references and outDir
- Break buffer/services cycle via buffer-local service interfaces
- Move cell types, keyboard/unicode types, TaskQueue, and TerminalOptions
- Exclude *.test.ts from composite builds; fix parser IDisposable imports

Co-authored-by: Daniel Imms <Tyriar@users.noreply.github.com>

src/common/base/TerminalOptions.ts

@@ -0,0 +1,13 @@
+/**
+ * Copyright (c) 2018 The xterm.js authors. All rights reserved.
+ * @license MIT
+ */
+
+import { ITerminalOptions as IPublicTerminalOptions } from '@xterm/xterm';
+
+// TODO: The options that are not in the public API should be reviewed
+export interface ITerminalOptions extends IPublicTerminalOptions {
+  [key: string]: any;
+  convertEol?: boolean;
+  termName?: string;
+}