drscheme:teachpack:install-teachpacks in DrScheme Tools Functions

• (drscheme:teachpack:install-teachpacks teachpack-cache) -> void?
     teachpack-cache : drscheme:teachpack:teachpack-cache?

  Installs the teachpack cache in the current namespace. Passing 'drscheme:teachpacks to preferences:get returns the user's currently selected TeachPacks.