Adding another lib into the productset system

[Friedrich W. H. Kossebau]

Am Mittwoch, 1. Mai 2013, 00:03:24 schrieb Jaroslaw Staniek:
> Hello Freidrich,
> By the way I have one question, in /CMakeLists.txt there's line
> 
> calligra_define_product(KEXI "Full Kexi (for Desktop)"  NEEDS KEXI_APP
>  WANTS PLUGIN_KEXI_SPREADSHEETMIGRATION)
> 
> I'd like to disable the optional PLUGIN_KEXI_SPREADSHEETMIGRATION for
> my KEXI product
> in my kexi.cmake. Any idea how can I do it cleanly?

Just list KEXI_APP instead of KEXI in kexi.cmake.

The initial idea with the product set was to have everything as opt-in, and no 
support for opt-out.

That BUILD_x=OFF still works is just a backward compatibility for now. Seems I 
should also add a big warning for that :)

Those current products with WANTS dependencies are more kind of convenience 
products. Possibly WANTS should really be only available for meta-products. 
After all the global productset is also a product with lots of WANTS. So I 
guess I should propose a patch which adds productsets next to products. 
Productsets are listing of wanted products (and productsets), while products 
only can have needed internal dependencies on other products. 

Putting this close to the top of my TODO list.

Cheers
Friedrich