Segments index and forms improvements

We've made some improvements to the segments index and the segment forms.

Segment index improvements

• When creating a dynamic segment, a loading indicator and status will now appear in the index.

• The Publication column is now enabled by default on segment index.
• We've added an ID column with name support to the segments index.

Segment form improvements

• Changed the default segment type to dynamic in the create segment form.

• Added partner select to step 3 in the segment import form.
• Fixed segment import failure on CSV files in Firefox.