bspm 0.5.0

• New function moveto_sys() moves existing user packages to the system
  library to avoid package shadowing; the associated script mass_move
  enables mass-calling this function for several users and/or libraries to
  facilitate bspm deployment in multitenant servers (#60 addressing #59).
• New function shadowed_packages() analyzes the library tree and reports
  which packages, one per row, are shadowed by others (#62 addressing #58).
• Add new options(bspm.version.check=FALSE) (true by default) to globally
  enable binary-source installation type (#61).
• Add a specific manual page bspm-options documenting all supported options.
• Add support for the installation of binary Suggests and Enhances if they are
  supplied to the dependencies argument of install.packages.
  LinkingTo now is omitted for binary packages as documented (#32).