Add footer with page creation time and cgit version on all pages

Signed-off-by: Lars Hjemli <hjemli@gmail.com>

cgit.css

@@ -447,3 +447,9 @@ span.age-months {
 span.age-years {
 	color: #bbb;
 }
+div.footer {
+	margin-top: 0.5em;
+	text-align: center;
+	font-size: 80%;
+	color: #ccc;
+}

ui-shared.c

@@ -443,6 +443,9 @@ void cgit_print_docstart(struct cgit_context *ctx)
 
 void cgit_print_docend()
 {
+	html("</div><div class='footer'>generated ");
+	cgit_print_date(time(NULL), FMT_LONGDATE);
+	htmlf(" by cgit %s", cgit_version);
 	html("</div>\n</body>\n</html>\n");
 }