Remove the external fonts usage

This is a radical (and simple) solution
to #853, #399, #439, #174 and partially #712.

airsonic-main/src/main/webapp/WEB-INF/jsp/head.jsp

@@ -12,8 +12,6 @@
 <!-- Included before airsonic stylesheet to allow overriding -->
 <link type="text/css" rel="stylesheet" href="<c:url value="/script/mediaelement/mediaelementplayer.min.css"/>">
 <link rel="stylesheet" href="<c:url value="/${styleSheet}"/>" type="text/css">
-<link rel="stylesheet" href="https://fonts.googleapis.com/css?family=Ubuntu&subset=latin,cyrillic-ext,greek-ext,greek,latin-ext,cyrillic" type="text/css"/>
-<link rel="stylesheet" href="https://fonts.googleapis.com/css?family=Roboto:400,300,400italic,500,300italic,500italic,700,700italic,100,100italic" type="text/css"/>
 <title>Airsonic</title>
 
 <!-- Import Mousetrap and enable shortcuts if necessary -->

airsonic-main/src/main/webapp/style/default-without-mediaelement.css

@@ -84,16 +84,16 @@ body {
 }
 
 body, form, label, table, a {
-    font-family: 'Roboto', arial, sans-serif;
+    font-family: arial, sans-serif;
 }
 
 h1, h1 a {
-    font-family: 'Ubuntu', arial, sans-serif;
+    font-family: arial, sans-serif;
     font-weight: normal;
 }
 
 h2, h2 a, .topHeader a {
-    font-family: 'Roboto', arial, sans-serif;
+    font-family: arial, sans-serif;
     font-weight: normal;
 }