Update index for salesforce_queue and salesforce_genmap_record_map

The index for both is the drupal unique identifier
Remove exportable from record entity. Makes no sence as a content object.
Ensure table default value and not null instruction is correct
Reorder column to be same as other similar columns in other modules
Rename 'salesforceMax' to 'sfMaxBatchSize'
Misc doc fix
Fix variable clash