Bug 25852: Improve C4::Creators::Lib reliability under plack

Bug 25852: Improve C4::Creators::Lib reliability under plack

This is certainly a major issue that leads to many side-effects.
Under plack, the structure of the default values are not handled
correctly.
Package variables are used to store stuff like the "layout type". They
are complex structures (arrays of hashes) and returned without being
copied.
When the caller (the controller script) retrieve them then modify the
returned structures, it actually modifies the package's variables.

One of the issue is:
Create a new layout
The script retrieve a structure with all "selected" flags are set to 0
It select the first one as default (BAR as selected => 1)
The user creates the new layout and will selected BIBBAR (for instance)
If you then edit this new layout, the script will retrieve the
"label_types" and set "selected" for BIBBAR. However BAR is still
selected!
The UI receives 2 selected and display the first selected one that has
the selected option.

Test plan:
1. Create a layout type for Barcode/Biblio
2. Choose fields to print and size of font
3. Save
4. Edit existing Layout
=> Withtout this patch "Barcode" is the preselected option
=> With this patch applied, the correct "Barcode/Biblio" option is
selected

Signed-off-by: Kelly McElligott <kelly@bywatersolutions.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>