Add quick link to add child category in show page

In the show page of a category, add a link to quickly
add a child category. The form will preselect the
parent category already for the new category.

Signed-off-by: Joan Tiffany Siy <joan@teamcodeflux.com>
Update edit form to use simple form

Set the form action and remove extra links.

Signed-off-by: Joan Tiffany Siy <joan@teamcodeflux.com>
Implement autocomplete feature to select parent category

Using JQuery UI's autocomplete function, this will
display query results underneath the field in a list
after the user has typed at least 3 characters in the
parent field.

Signed-off-by: Joan Tiffany Siy <joan@teamcodeflux.com>