Ingest pipeline feature processor dropdown

[BigFunger]

Replaces #7146 (please see comments in this issue for details)
Fixes #7061

Now targets the feature/ingest-pipeline feature branch

Additional changes:

• Moved the processor select into its own directive
• Modified the box-shadow of the dropdown-menu to address a bug in safari
• Changed all less variable names that started with @settings-filebeat-wizard to start with @settings-add-data-wizard instead

Edit 2016-5-31:
I modified the dependency from angular-ui-select' toui-select'. angular-ui-select was a clone of the official ui-select dependency and has not been updated.

[Bargs]

Another weird quirk, this time it happens in chrome as well. When the select box is near the bottom of the page so that the dropdown opens above it, filtering causes the result to float part way up the page.

[Bargs]

@BigFunger code looks good. Just need to resolve the above issue.

[BigFunger]

jenkins, test it

[Bargs]

Pending tests passing, LGTM

[Bargs]

🎉 🎉 🎉 🎉 🎉