WIP: Add embed button config entity
Add EmbedButton configuration entity
Add default entity and cleanup interface
Add help text for the settings page
Add commands and buttons for specific entities
Fix typo in function names
Use getButtonImage method to get url of the button icon
Merge branch '8.x-1.x' into entity-embed-config-entity
Use generic command for all entities
Cleanup code
Sanitize values from user input
Make the entity_embed.dialog route require button entity
Modify CKEditor plugin to use embed button in url
Rename name of admin permission to better convey its meaning
Rename data attribute: data-button-entity to data-embed-button
Declare class properties
Remove dead code
Fix travis failures based on suggestion by @berdir
Remove un-necessary explicit upcasting of config entity
Fix coding standards