Support public visibility of development ('private') components

[twagoo]

https://trac.clarin.eu/ticket/571

Note: this concerns a partial implementation of the feature described by #142

'''Description:''' There should be an option to mark '''private (either group or individual user)''' components and profiles as '''publicly visible'''. The owner(s) of a component decide on this state. Components marked as such should be visible in ''both'' the list of public components/profiles (but only if enabled by the viewing user) and in the user's/group's private list.

• Add a property representing 'public visibility' to components and profiles (i.e. change model + database schema).
  Note: The 'public' property should remain untouched (will be partly replaced by a 'status' property in CMDI 1.2, see #142).
• Support this in the REST backend: /registry/components?userSpace={userSpace}&showDraft={showDraft}
  (defaults: {userSpace}=false; {showDraft}=false (has no effect when userSpace=true))
  pseudo-sql (conceptual, does not have to be implemented in one query):

select * from components 
   where 
      "isPublic" != userSpace AND (!userSpace OR "owner" = uid)
      OR 
        !userSpace AND showDraft AND "publiclyVisible" = TRUE

• Add a button to toggle the 'publiclyVisible' property of a component (probably next to move to group)
• In the UI, add a checkbox to the ''view'' of public components or profiles that binds to the 'showDraft' option, allowing the user to filter out (default behaviour) draft components
• Add a clear indication (e.g. DRAFT) of this status in the components/profiles table!

[twagoo]

Components and profiles can be published with 'development' or 'production' status as of 1f60890. TODO: do not allow publication as deprecated.