ior: new attributes and improvements
ior: new attributes and improvements

The following change aimed to shrink YAML of IOR campaigns
run at BBP.

* api_file_mode_options: a dictionary to specify
additional options according to API and file mode.
Default value:
  - if fpp => '-f'
  - if MPIIO and onefile => -c
  User can override this feature in YAML
* properly handle path with prefix (like `ime://`)
  in `pre_execute` hook.
* `clean_path`: new boolean option to remove test directory
if it already exists. Default is True.
* `repetitions`: number of repetitions of test

tristan0x/hpcbench,tristan0x/hpcbench,tristan0x/hpcbench