UI fixes in SessionRestoreErrorDialog

* Make the 'delete my data' button not the default
 * Make it red
 * Give it a confirmation dialog
 * Remove the 'cancel' button: what does it mean to cancel an error?
   In this case, it tried again and almost certainly got the same error.
 * Remove the top-right 'x' and don't cancel on esc for the same reason.
 * Move 'send bug report' to a button rather than a 'click here' link
 * Add a 'refresh' button which, even if it's no more likely to work,
   will at least look like it's doing something (it's mostly so if you
   don't have a bug report endpoint, there's still a button other
   than the one that deletes all your data).

src/components/views/dialogs/BaseDialog.js

@@ -1,5 +1,6 @@
 /*
 Copyright 2017 Vector Creations Ltd
+Copyright 2018 New Vector Ltd
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -41,6 +42,13 @@ export default React.createClass({
         // cancelled (from BaseDialog, this is always false).
         onFinished: PropTypes.func.isRequired,
 
+        // Whether the dialog should have a 'close' button that will
+        // cause the dialog to be cancelled. This should only be set
+        // to true if there is nothing the app can sensibly do if the
+        // dialog is cancelled, eg. "We can't restore your session and
+        // the app cannot work".
+        hasCancel: PropTypes.bool,
+
         // called when a key is pressed
         onKeyDown: PropTypes.func,
 
@@ -59,6 +67,12 @@ export default React.createClass({
         contentId: React.PropTypes.string,
     },
 
+    getDefaultProps: function() {
+        return {
+            hasCancel: true,
+        };
+    },
+
     childContextTypes: {
         matrixClient: PropTypes.instanceOf(MatrixClient),
     },
@@ -77,7 +91,7 @@ export default React.createClass({
         if (this.props.onKeyDown) {
             this.props.onKeyDown(e);
         }
-        if (e.keyCode === KeyCode.ESCAPE) {
+        if (this.props.hasCancel && e.keyCode === KeyCode.ESCAPE) {
             e.stopPropagation();
             e.preventDefault();
             this.props.onFinished(false);
@@ -104,11 +118,11 @@ export default React.createClass({
                 // AT users can skip its presentation.
                 aria-describedby={this.props.contentId}
             >
-                <AccessibleButton onClick={this._onCancelClick}
+                { this.props.hasCancel ? <AccessibleButton onClick={this._onCancelClick}
                     className="mx_Dialog_cancelButton"
                 >
                     <TintableSvg src="img/icons-close-button.svg" width="35" height="35" />
-                </AccessibleButton>
+                </AccessibleButton> : null }
                 <div className={'mx_Dialog_title ' + this.props.titleClass} id='mx_BaseDialog_title'>
                     { this.props.title }
                 </div>