Retrace branch merge

[Karel Klic]

Hi,

I am going to merge the retrace branch to our git master, so we can 
integrate the retrace client into ABRT, develop retrace server in more 
visible way, and eventually make a release.

The merge should go smoothly -- see the attached patch showing the 
differences between the branches.

Feel free to review the code. I know that the abrt-retrace-client.c 
needs some de-duplication work.

Karel