daemon: deal with missing 'executable' file

Problem directories may not cotain 'executable' file (e.g. koops).

abrt-handle-event tries to compare executables of dump directories before
checking for duplicates. Unfortunately, the executable of handled
directory is not loaded with the "fail quietly" flag and the error
message messes up logs.

Related rhbz#1105316
tmp
fix major problems
fix paths
Add manpage
manpage to spec
fix usage string
Add MCE configuration option