GH95 - custom icons

#95
this class behavior is the following:
by default, shows custom + default icons; if showOnlyRepositoryCustomIcons, shows only custom icons.

so, we need:
- a method that gets icons from server = getCustomIcons()
- a method that handles the result = getCustomIconsHandler()
- a method that adds a list of icons as children = addIcons(list:IList, areCustomIcons:boolean)