refractor: login module (#283)

* Refractor components.
* Shift language and footer component to shared module.
* Replace mat-icons by font-awesome icons.
* Add comments.

Fixes #284

src/app/shared/icons.module.ts

@@ -5,18 +5,31 @@ import { NgModule } from '@angular/core';
 import { FontAwesomeModule } from '@fortawesome/angular-fontawesome';
 import { library } from '@fortawesome/fontawesome-svg-core';
 import {
+  faCheckCircle,
+  faEye,
+  faEyeSlash,
   faFileUpload,
-  faSearch
+  faLock,
+  faSearch,
+  faUserCircle,
+  faUserShield
 } from '@fortawesome/free-solid-svg-icons';
 
 /** Add icons to the library for convenient access in other components. */
 library.add(
+  faCheckCircle,
+  faEye,
+  faEyeSlash,
   faFileUpload,
-  faSearch
+  faLock,
+  faSearch,
+  faUserCircle,
+  faUserShield
 );
 
 /**
  * Icons Module
+ *
  * Angular Font Awesome module is exported here.
  */
 @NgModule({