Fix naming of build artifacts to bitcoin-abc-...

Summary:
As per T83, build artifacts (tarball produced by
make dist and the packages produced by gitian builds
are now named bitcoin-abc-XXXXXXXXXXXXXX
where the XXXXXXXXX part includes the version number
and followed by more specifics such as platform / architecture
in case of gitian build products.

Test Plan:
configure
make check
run gitian builds and check produced tarballs are named
as expected and also their contents are structured with bitcoin-abc-<version> folders

Ran the GUI executable and checked for interference of PACKAGE
name change, but didn't find any negative effects.

More testing of build products (e.g. installable packages on Windows/OSX
is needed) to determine whether they work right.

Reviewers: #bitcoin_abc, deadalnix

Reviewed By: #bitcoin_abc, deadalnix

Maniphest Tasks: T83

Differential Revision: https://reviews.bitcoinabc.org/D482