Save information that data were exported

[scardinius]

Related to #157

[deepak-srivastava]

We need to make sure it doesn't break the site for civi versions before 5.8. At the moment export fails for earlier versions of civi with the error:

One solution could be providing default values for last 2 new argument in the export hook. That would also mean that the entity export methods don't action anything if component table or ids are missing.

[scardinius]

@deepak-srivastava I added checking of version. Those new variables are available from 5.8.0
https://docs.civicrm.org/dev/en/latest/hooks/hook_civicrm_export/#availability

[deepak-srivastava]

@scardinius Thanks, but that alone won't fix it because number of arguments in gdpr_civicrm_export() still differ - 4 vs 6, which is what php is complaining about.

[scardinius]

@deepak-srivastava ah, yes, you're right. Added

[deepak-srivastava]

Thanks @scardinius 👍