Fix incorrect reference to FieldControl events

This is part of the class definition, and therefore defined on
the prototype.
Add ButtonSelect view

The view provides select-like functionality, but provides a more
consistent look and feel (with buttons and other dropdown-based
components). In addition, the behavior can be customized as well as
the dropdown options themselves.
Add basic changelog structure
Move UI-based components to cilantro.ui module
Simplify gallery style
Change concept panel to display a list

This is consistent with the columns modal and enables display
all filtered choices rather than only the max allowed in a dropdown.

One caveat is that categories are no longer collapsed.