base64: ignore -i as promised

Add a quoted-printable encoder/decoder

As an example:
printf 'We don=27t know what to do with other=20worlds.=0D=0A' \
| bintrans qp -u

Differential Revision: https://reviews.freebsd.org/D34933

Reviewed by: debdrup (manpage)

Add the base64 command using b64encode and b64decode

Various scripts expect the base64 command to be present. We've had the
code and it's been exposed as b64encode/b64decode, but it wasn't widely
known under these names and the syntax is much different.

Reviewed by: delphij
Differential Revision: https://reviews.freebsd.org/D32945

bintrans: move files to a new directory

And reflect the change in various places.