erp5_pdm: use preferred category child item list method in my_variation_category_list field library.

Python script needs to be recompiled when they comes from a change of
class. This was done when business template was installing scripts, but
not when automatic migration from old catalog to new catalog was done.
So make sure to call _compile directly in changeObjectClass to make sure
Python Scripts would always work after a change of class.

Replace the airplane icon by a search button if not value is set on the field.
This make it more usable on mobile, where it's easier to browse than typing text.

Regression introduced by nexedi/erp5@cf1a0610

getSecurityQuery returns None when caller is superuser. Avoid passing it
to buildSQLQuery, as it would mistake security_query for a column name.

Float fields are needed to round amounts.
Also, discard empty form groups.
Also, make "hidden" the first group, so any created field gets hidden by default
(which is what we want for all listbox "editable" fields).
Also, remove overrides which seem unneeded for report appearance:
- "lines" is not used for OD* rendering
- "columns" is already the same as in original field
"editable_columns" is used in odt (and maybe in ods, unclear), but
inconsistently with its intended use... so leave it, sadly.

Fixes bug /#/bug_module/20171211-153B610

/reviewed-on !526

Removed code from not implemented and not needed compatibility layer.

/reviewed-on !525