caps: Added a capability check has_sharedfile()

refs #11643
has_sharedfile() now used in the add form wizard

refs #11643
sharedfile: moved to constants, remove option if < GANET26

refs #11643
Merge branch 'enhancement/11643' into develop

* enhancement/11643:
  sharedfile: moved to constants, remove option if < GANET26
  has_sharedfile() now used in the add form wizard
  caps: Added a capability check has_sharedfile()