Fault injection summary

During fault injection, each run is now labeled with its index to provide the user a progress report. A brief summary is also printed after all runs are completed, in the form of a histogram of process exit codes. Here is a small example:

```
99:  /home/shaden/src/inject/test/llfi/sum-faultinjection.exe 50
	 program finish -11
	 time taken 1 

========== SUMMARY ==========
Return codes:
    0:    34
    1:     4
    2:    32
   16:     1
  -11:    27
   -7:     2
```