Conditional tabs integration

[bUxEE]

Added integration for "show_on_cb" option already present in CMB2 field options to enable conditional tabs.

[pgroot91]

I have tested the branch and have some problems with the implementation.

1. You need to have the "show_on_cb" specified on your tabs or you will get the following notices.

Notice: Undefined index: show_on_cb in C:\xampp\htdocs\dev1\wp-content\plugins\my-plugin\includes\cmb2-tabs\inc\cmb2-tabs.class.php on line 67 Notice: Undefined index: show_on_cb in C:\xampp\htdocs\dev1\wp-content\plugins\my-plugin\includes\cmb2-tabs\inc\cmb2-tabs.class.php on line 79

2. My bad! 👍