Validation, settings UI cleanup and different settings models, oh my

New: Download client UI matches other settings
Fixed: Prevent drone factory folder from being set to invalid paths/root path for series
Fixed: Switching pages in settings will not hide changes
Fixed: Test download clients
Fixed: Settings are validated before saving

src/UI/.idea/jsLinters/jshint.xml

@@ -8,16 +8,16 @@
     <option es3="false" />
     <option forin="true" />
     <option immed="true" />
-    <option latedef="true" />
     <option newcap="true" />
     <option noarg="true" />
     <option noempty="false" />
     <option nonew="true" />
     <option plusplus="false" />
     <option undef="true" />
-    <option unused="true" />
     <option strict="true" />
     <option trailing="false" />
+    <option latedef="true" />
+    <option unused="true" />
     <option quotmark="single" />
     <option maxdepth="3" />
     <option asi="false" />