Remove redundant spaces when creating a segment

Description

Steps to reproduce

1. Create a filter definition whose category is "PFDs".
2. Create another filter whose category is "PFDs ". (note extra space)
3. Create a third filter whose category is " PFDs ". (note extra spaces)
4. Go to Insight/Segments.
5. Click the Create a segment button.

Actual:
Three categories with the same name ("PFDs") are displayed.

Expected
When creating filter definitions, category name should be trimmed.