Specs are using doubles

Apply constructor changes

Add specs for SystemNotes::IssuablesService

Fix misspelled file name

Add parameter exclude_project to shared sample

So duplicate definition could be removed.

Use let_it_be instead of set

Remove one superfluous redefinition

Move service definition to top of specs

Use let_it_be instead of set

Add new line

Remove obsolete method (moved to SystemNotes::IssuablesService)

Remove obsolete methods from SystemNoteService

(moved to SystemNotes::IssuablesService)

Replace doubles with noteable, project and author