refs https://github.com/TryGhost/Team/issues/1290
- when set to `false` prevents the dropdown opening when it would only contain the "Type to search" message
- uses the `@extra` hash param. Would be preferable to be able to use `@searchMessage=""` but ember power select doesn't pass the searchMessage argument through to the trigger
refs https://github.com/TryGhost/Team/issues/1290
- switched to using our `gh-input-with-select/trigger` power select trigger to get a search input with select
- kept the replacement with a button once a selection is made for easier clearing of the selection
refs https://github.com/TryGhost/Team/issues/1219
- added `dropdown.closeDropdowns()` to the `{{movable}}` modifier when dragging starts
- updated ember-power-select derived inputs to close their dropdowns when the dropdown service triggers it's `'close'` event
refs https://github.com/TryGhost/Team/issues/993
- added calls to `onFocus()` and `onBlur()` arguments inside the trigger when the input is focused/blurred so that the active class is correctly applied by ember-power-select
- removed unnecessary mousedown propagation cancellation, it was a copied from `<GhTokenInput>` where extra mouse handling is necessary for buttons inside tokens
- updated `.gh-input-with-select` styles to add the border when active
refs https://github.com/TryGhost/Team/issues/1009
- setting `tabIndex="-1"` on the trigger prevents the trigger container receiving focus rather than the container input element (fixes general tabbing in and out)
- added extra blur handling to the input element so that it is not left in an open dropdown state when tabbing out
refs https://github.com/TryGhost/Team/issues/973
- added `@showCreate` option to `<GhInputWithSelect>` that enables the create option without having to pass a function in `@showCreateWhen`
- fixed autofocus not focusing input element in `<GhInputWithSelect>` when `autofocus="true"` isn't enough by itself
- updated `selectOrCreate` in `<GhInputWithSelect>` to trigger `onChange` if it's passed in rather than `onInput`
- swapped input in labs snippet input to `<GhInputWithSelect>`
- added actions for updating a snippet when an existing snippet is selected
- added action to editor control for saving an updated snippet
refs https://github.com/TryGhost/Team/issues/987
- `<GhInputWithSelect>` acts as a typical text input element but will also show options that are filtered whilst typing. Useful for inputs where there should be suggestions or the ability to choose an existing option
- updated `<GhSearchInput>` to use the renamed and slightly modified trigger
