kohabug 2022 - fixed fine and issuing rules editors

kohabug 2022 - fixed fine and issuing rules editors

Because of the way that the older fine and issuing
rule editors generate the HTML form, if a branch code,
patron category code, or item type code happened to have a
'-' or '.', the HTML form would not be parsed properly, thus
adding an implicit (rather than explicit) limit on the
characters allowed in one of those codes.

This fix removes this limitation by Base64-encoding the codes
when constructing the names for the <input> elements.

Two functions are added to C4::Koha:

  str_to_base64() - UTF-8 string to Base64
  base64_to_str() - reverse

Signed-off-by: Joshua Ferraro <jmf@liblime.com>