Fix the translations for 'conversation'

There are old translations containing the word 'conversation' instead of the term 'answer'. From a consistency point of view this needs to be fixed: review all translations and replace the terms.

There are 12 entries that contain 'conversation' instead of 'answer':
conversations.title
conversation.delete.done
conversation.delete.success
conversation.delete.failed
conversation.edit.failed
conversation.delete.title
conversation.edit.title
conversation.like.button.tooltip
conversation.like.score.tooltip

Also deletion of Topic and Answers should be symmetric so
conversation.delete.title=Delete Answer (to be symmetric with conversation.forum.delete)
conversation.edit.title=Edit Answer (to be symmetric with conversations.forum.edit)