Image stuff (#77)

Features
---------
Image to PDF supports multiple images, stretching and auto rotation
File inputs now only search for wanted file type
Settings now has a zip range so it can zip if you have more than x downloads (default 4)

extras
---------
DevTools support for easier development
Fix for temporary files for thread safety

src/main/resources/templates/rotate-pdf.html

@@ -16,7 +16,7 @@
                         <h2 th:text="#{rotate.header}"></h2>
 
                         <form action="#" th:action="@{rotate-pdf}" th:object="${rotateForm}" method="post" enctype="multipart/form-data">
-                            <div th:replace="~{fragments/common :: fileSelector(name='fileInput', multiple=false)}"></div>
+                            <div th:replace="~{fragments/common :: fileSelector(name='fileInput', multiple=false, accept='application/pdf')}"></div>
                             <input type="hidden" id="angleInput" name="angle" value="0">
 
                             <div id="editSection" style="display: none">