Migrate Clipboard handler to TypeScript

Also apply JavaScript rules in `.editorconfig` in TypeScript files as well.

Part of #335

src/test/clipboard-test.js

@@ -1,18 +0,0 @@
-var assert = require('chai').assert;
-var Terminal = require('../xterm');
-var Clipboard = require('../handlers/Clipboard');
-
-
-describe('evaluateCopiedTextProcessing', function () {
-  it('should strip trailing whitespaces and replace nbsps with spaces', function () {
-    var nonBreakingSpace = String.fromCharCode(160),
-        copiedText = 'echo' + nonBreakingSpace + 'hello' + nonBreakingSpace,
-        processedText = Clipboard.prepareTextForClipboard(copiedText);
-
-    // No trailing spaces
-    assert.equal(processedText.match(/\s+$/), null);
-
-    // No non-breaking space
-    assert.equal(processedText.indexOf(nonBreakingSpace), -1);
-  });
-});