[fix] oscar theme, remove inline style attributes (CSP compliants)

Inline styles are blocked by default with Content Security Policy (CSP).  Move
the rest of inline styles to CSS and correct the HTML template of the oscar
preference page.

Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>

searx/static/themes/oscar/less/logicodev/preferences.less

@@ -1,3 +1,15 @@
 .table > tbody > tr > td, .table > tbody > tr > th {
     vertical-align: middle !important;
 }
+
+.nav-tabs.nav-justified{
+  margin-bottom: 20px;
+}
+
+p {
+    margin: 10px 0;
+}
+
+input.cursor-text {
+    margin: 10px 0;
+}