This commit adds a new parameter on fields for list view and one2many.
The parameter name is "optional" and its values are "hide" or "show".
Columns of the list view which have the optional parameter set are
listed in a dropdown that can be toggled from the last cell of the
table header. The ones with optional set to "hide" are hidden by
default.
User choice is stored in local storage. If no saved parameter can be
found in local storage then the default value from the view is used.
Due to the overflow behavior of the responsive table, we were forced
to wrap the table-responsive div in yet another div. We changed the
o_list_view class on the table to o_list_table in order to reuse
the more generic o_list_view class on the top-most div. CSS rules
and selectors had to be updated according to this change.
Task-1902765
David Monjoie
88a26235ca