Add a new action generating 'machineid' problem element

This pull request is required for identification of RHEL systems reporting to the RH Customer Portal. Adding the 'machineid' element to problem data on Fedora is useless (might be useful in future) and it doesn't work, because SElinux prevents abrtd from reading /dev/mem (the produced AVC is not audited by default).

The following policy is required to test this pull request or you can temporarily configure selinux to be permissive:

```
policy_module(abrt-action-generate-machine-id-policy, 1.0)

require {
        type memory_device_t;
        type abrt_t;
        class capability sys_rawio;
        class chr_file { read open };
}

#============= abrt_t ==============
allow abrt_t memory_device_t:chr_file { read open };
allow abrt_t self:capability sys_rawio;
```