Dan Harrin cd86c62b94
Relation Manager Customisation Improvements (#4444)
This change allows for easy customisation of the relation manager titles and toolbar buttons.

For buttons - define your custom strings directly in the standard `toolbarButtons` syntax...

```
toolbarButtons:
    create: acme.blog::lang.subcategory.CreateButtonText
    delete: # omit the string to fall back to the default button text
```

...and the old syntax still works...

```
toolbarButtons: create|delete
```

For titles - define different strings for each mode (form, list or pivot)...

```
title:
    form: acme.blog::lang.subcategory.FormTitle
    list: acme.blog::lang.subcategory.ListTitle
```

This feature provides developer convenience, for example in this situation where I have a relation manager that is used to assign user permissions to a project:
Before
![Screenshot 2019-07-10 at 09 28 22](https://user-images.githubusercontent.com/41773797/60953626-6bc0de80-a2f5-11e9-8001-04e816ad6967.png)
After
![Screenshot 2019-07-10 at 09 32 51](https://user-images.githubusercontent.com/41773797/60953773-b9d5e200-a2f5-11e9-93a9-69238ea696aa.png)

This PR contains no breaking changes.
2020-03-27 12:56:07 -06:00
..