Bugfix: LDC-471 - flag links not showing in panelizer node links pane

## Ready State: Yes

Relates to jira bug https://imagex.atlassian.net/browse/LDC-471

On further investigation I found panelizer exports the entity view mode as "page_manager" but doesn't provide it to be customised. In the case of the flag module where you must select views modes to display flag links in or place them manually it meant you couldn't select the "page_manager" view mode so flag links wouldn't show.
This fix, assumes view mode "full" for flag links only if the view mode is "page_manager".

As this covers flag links in general I placed it in this feature rather than recreate the fix for each imagex feature providing flags.

## Requirements & Dependencies

None

## Deployment Instructions

* Merge code.
* Enable module `imagex_content_like`
* Clear caches with `drush cache-clear all`

## Usage/Test Instructions

* Enable module `imagex_content_like`
* Create some content that uses panelizer and has the node links pane within the layout
* Ensure flag links show & are functional