[Toaster] Testcases for Custom Image -- Adding and Removing Packages

[Cruz, Libertad]

Hello,

I have written the following TC for customise images functionality.


https://bugzilla.yoctoproject.org/tr_show_case.cgi?case_id=1439
https://bugzilla.yoctoproject.org/tr_show_case.cgi?case_id=1440
https://bugzilla.yoctoproject.org/tr_show_case.cgi?case_id=1441
https://bugzilla.yoctoproject.org/tr_show_case.cgi?case_id=1444

I have applied Belen's feedback, any other feedback will be highly appreciated. 



Best Regards
Libertad G.