Added hooks to hide the "send to Salesforce" button and checkbox on the entries view/edit screen.

Use: `add_filter( 'gf_salesforce_show_manual_export_button', '__return_false' ); //hide button & checkbox`

git-svn-id: https://plugins.svn.wordpress.org/gravity-forms-salesforce/trunk@861736 b8457f37-d9ea-0310-8a92-e5e31aec5664
= 2.6.4 (February 20, 2014) =
* Fixed (API Version): Live Remote Field Mapping improvements
	- Fixed endless spinning
	- Empty options are better managed; shows "No Picklist Fields" message
	- Now shows an error message if the field cannot be used for Remote Field Mapping
	- Static PHP warning fixed when `WP_DEBUG` enabled

git-svn-id: https://plugins.svn.wordpress.org/gravity-forms-salesforce/trunk@861954 b8457f37-d9ea-0310-8a92-e5e31aec5664