Adding genfio tool : an fio job creator

Adding genfio tool : an fio job creator

Some fio users need to create multiple fio jobs to compare storage
device's performance on different workload.

genfio is made for creating series of fio jobs based on the following
parameters:
- a disk serie
- a block size serie
- the time each job shall run (default is 300 seconds)
- the expected IO patterns to perform (read,write,randread,randwrite)
- a parameter to define if disks shall be tested one after the other or
  simultaneously

Based on all this parameters, a single fio script file will be computed
to process all this workloads.

Example:
[user@localhost]: genfio -d sdb,sdc,sdd,sde -a -b 4k,128k,1m -r 100 -a
Generating localhost-4k,128k,1m-all-read,write,randread,randwrite-sdb,sdc,sdd,sde.fio
Estimated Time = 6000 seconds : 1 hour 40 minutes

If the user run "fio
localhost-4k,128k,1m-all-read,write,randread,randwrite-sdb,sdc,sdd,sde.fio",
it will run:
- a sequential bench on /dev/sdb /dev/sdc /dev/sdd /dev/sde
    block size = 4k with read,write,randread,randwrite tests
    ETA ~ 4 tests * 4 disks * 100 seconds

- a sequential bench on /dev/sdb /dev/sdc /dev/sdd /dev/sde
    block size = 128k with read,write,randread,randwrite tests
    ETA ~ 4 tests * 4 disks * 100 seconds

- a sequential bench on /dev/sdb /dev/sdc /dev/sdd /dev/sde
    block size = 1m with read,write,randread,randwrite tests
    ETA ~ 4 tests * 4 disks * 100 seconds

- a parallel bench on /dev/sdb /dev/sdc /dev/sdd /dev/sde
    block size = 4k with read,write,randread,randwrite tests
    ETA ~ 4 tests * 100 seconds

- a parallel bench on /dev/sdb /dev/sdc /dev/sdd /dev/sde
    block size = 128k with read,write,randread,randwrite tests
    ETA ~ 4 tests * 100 seconds

- a parallel bench on /dev/sdb /dev/sdc /dev/sdd /dev/sde
    block size = 1m with read,write,randread,randwrite tests
    ETA ~ 4 tests * 100 seconds

For each job of this fio script, bandwidth & iops logs file will be
generated allow further investigations or plotting.