Pass by value to get_filesystem_object()

get_filesystem_object() takes a constant reference to a FILESYSTEM, but
FILESYSTEM is just an enumeration.  So that's a pointer to a constant
int.  Just pass by value instead.
Comment and re-order FILESYSTEM enumeration type
Add supported_filesystem() predicate method (#738471)

Helper to check whether a recognised file system type is supported by
GParted or not.  Supported means there is an implementation class and
will appear in the File System Support dialog.

Make supported_filesystem() a static member function so that it can be
called without a class object so that GParted_Core::GParted_Core()
initialiser isn't called multiple times.  This requires FILESYSTEM_MAP
to become a static member variable too.

Bug #738471 - ReFS file system is not recognised
Use supported_filesystem() predicate (#738471)

Use GParted_Core::supported_filesystem() to remove the need to
explicitly list the growing number of recognised, but otherwise
unsupported, file system signatures in multiple places.

Bug #738471 - ReFS file system is not recognised
Recognise ReFS file system (#738471)

Only recognises ReFS file system.  No other actions are supported.
Requires blkid from util-linux >= 2.24.

Bug #738471 - ReFS file system is not recognised
Rework population of the create new partition file system list

Simplify how the list of file system types is populated in the Create
New Partition dialog.  Change from copying everything and removing
unwanted items to only copying required items.  Makes the code simpler
and therefore easier to understand.