When adding a new index, exclude fields that have already been added from the drop down list. Part of issue #928.
When adding a new index, exclude fields that have already been added from the drop down list. Part of issue #928.

CoolSwitcher/sequelpro,josegonzalez/sequelpro,josegonzalez/sequelpro,treejames/sequelpro,leichunxin/sequelpro,Jellyfrog/sequelpro,eric-seekas/sequelpro,Jellyfrog/sequelpro,leichunxin/sequelpro,CoolSwitcher/sequelpro,chenbk85/sequelpro,chenbk85/sequelpro,abhibeckert/sequelpro,kaneshin/sequelpro,josegonzalez/sequelpro,leichunxin/sequelpro,treejames/sequelpro,dnl-jst/sequelpro,eric-seekas/sequelpro,eric-seekas/sequelpro,kaneshin/sequelpro,kaneshin/sequelpro,chenbk85/sequelpro,josegonzalez/sequelpro,dnl-jst/sequelpro,dnl-jst/sequelpro,abhibeckert/sequelpro,treejames/sequelpro,leichunxin/sequelpro,treejames/sequelpro,CoolSwitcher/sequelpro,Jellyfrog/sequelpro,kaneshin/sequelpro,Jellyfrog/sequelpro,eric-seekas/sequelpro,chenbk85/sequelpro,abhibeckert/sequelpro,abhibeckert/sequelpro,dnl-jst/sequelpro,CoolSwitcher/sequelpro