[151] update README, configuration and defaults (4-2-stable)

[trel]

we can point to the policy-based implementation(s) once they are released (and re-use a lot of the text i'm removing here).

[trel]

@ccacciari does this make it clearer?

[ccacciari]

Yes, it is clearer. Maybe is it possible to add an example of rule to invoke it? Looking at the slides of the past year, I found an example, but it did not work:

$ cat tiering-1.r 
{   
  "rule-engine-instance-name": "irods_rule_engine_plugin-unified_storage_tiering-instance",
  "rule-engine-operation": "apply_storage_tiering_policy",   
  "delay-parameters": "<PLUSET>1s</PLUSET><EF>1h DOUBLE UNTIL SUCCESS OR 6 TIMES</EF>",   
  "storage-tier-groups": [       
                           "example_group_g2",       
                           "example_group"   
                         ]
}
INPUT null
OUTPUT ruleExecOut
$ irule -r "irods_rule_engine_plugin-unified_storage_tiering-instance" -F tiering-1.r 
remote addresses: xxx.yyy.xx.xxx ERROR: rcExecMyRule error.  status = -66000 SYS_NOT_SUPPORTED

Thanks

[ccacciari]

Sorry my fault. I did not notice that the example is already there. It works.

[trel]

Excellent - thanks.