Standardize Move/Draw/Edit buttons across plugins

[pllim]

As suggested by @ejeschke in https://github.com/ejeschke/ginga/pull/506#issuecomment-306918787

I do think that the Move/Draw/Edit controls should be standardized (as much as possible) accounting for the different things that the plugins do. And LineProfile is perfectly compatible in this regard, but the controls are constructed differently and show up more widely spaced than in other plugins (because they end up in a GridBox rather than in an HBox). This is a minor point, but these types of minor inconsistencies can contribute to an overall sense of inconsistency for the application. So I would suggest that in a future work we either make these look like the others, or make the others look like these.