[Kernel] replace do_iterate with is_reconfigurable

Allows iterating through _all_ plugin options, while keeping same list of
options for the GUI.

Typed parameters have two extra fields:
- visible: must be synchronized with the Cmdline.visible field;
- reconfigurable: to be shown in the GUI's "Analyses" panel.

iter_on_plugins (and fold_on_plugins) operate over all plugin options