Change links to buttons

- more semantically accurate, will expose these as buttons to assistive technologies
- note: while having block-level elements like `<div>` inside a `<button>` is an html validation error, it does not affect functionality as long as there's no more structure inside it

src/popup/components/pop-out.component.html

@@ -1,5 +1,5 @@
 <ng-container>
-    <button (click)="expand()" appA11yTitle="{{'popOutNewWindow' | i18n}}">
+    <button type="button" (click)="expand()" appA11yTitle="{{'popOutNewWindow' | i18n}}">
         <i class="fa fa-external-link fa-rotate-270 fa-lg fa-fw" aria-hidden="true"></i>
     </button>
 </ng-container>

src/popup/components/send-list.component.html

@@ -1,4 +1,4 @@
-<a *ngFor="let s of sends" (click)="selectSend(s)" href="#" appStopClick title="{{title}} - {{s.name}}"
+<button type="button" *ngFor="let s of sends" (click)="selectSend(s)" appStopClick title="{{title}} - {{s.name}}"
     class="box-content-row box-content-row-flex">
     <div class="row-main">
         <div class="app-vault-icon">
@@ -47,4 +47,4 @@
             <i class="fa fa-lg fa-trash-o" aria-hidden="true"></i>
         </span>
     </div>
-</a>
+</button>