Filters / Pagination / Selectize

• Adds filters to different index views. (To be expanded to more views later.)
• Adds pagination to different index views using Kaminari. (To be expanded to more views later.)
• Adds Bootstrap theme for Kaminari.
• Adds selectize for different foreign key / association input fields. (To be expanded to more views later.)
• Adds performance optimized bulk insertion of fake student users to seeds.