Add a `object_sync_for_salesforce_change_pull_date_value` filter to allow developers to modify the datetime value that the SOQL query uses for pulling records from Salesforce.

[jonathanstegall]

What does this Pull Request do?

This allows developers to modify the value for the "last pull date" to any datetime value, including a datetime from before the plugin was activated.

How do I test this Pull Request?

• use the example filter to use an older date. the plugin will pull records based on it.