hob: progress bar changed to busy cursor when you open log file

-the first implementation for this bug used a progress bar, that is shown
during open file process; it revelead that the progress bar stops earlier
-now I have implemented using gtk.show_uri() method, that shows itself a
busy cursor when it opens a file;
-deleted the code for the first implementation

[YOCTO #2997]
Signed-off-by: Cristiana Voicu <cristiana.voicu@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
hob: Hob should display warnings generated during parsing

-now Hob catches the warnings generated during parsing, and after the parsing
is completed, if there are any warnings, it shows a bar that contains a message
with how many warnings has encountered, and a button "View warnings"
-when "View warnings" button is clicked, Hob shows a dialog with the warnings;
if there more than 1 warning, you can use "Previous" and "Next" button to see them

[YOCTO #3215]
Signed-off-by: Cristiana Voicu <cristiana.voicu@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>