Integrated old GPG replication patches

Integrates the following patches into the latest codebase (beta):

https://github.com/pecastro/musicbrainz-server/commit/f68c7575192a348dcd
c386404b7e56b5084a49ea

https://github.com/metabrainz/musicbrainz-server/compare/6a00461...mbh-1
53
Updated DBDefs declarations to use new style.

[CHG] Updated all "&DBDefs::"  to OO style refferences (DBDefs->).

[CHG] Commented out GPG_* options from the DBDefs.pm.sample to keep
inline with "Commented-out lines should generally have sane defaults"

[ADD] Added default values for all GPG_* keys into DBDefs/Default.pm.
By default, server will use no GPG signing/validation.
Updated code to use Try::Tiny
Updated signature process for replication packats and current database dumps

[CHG] Updated current database dump signatures to use detached
signatures, thus avoiding data duplication.

[CHG] Removed GPG_SIGNING_OPTIONS from the DBDefs keys in favour of the
existing --sign-with command line switch.

[CHG] Changed GPG binary name from /usr/bin/gpg to gpg, thus avoiding
"GPG not found" errors on systems where gpg is installed in
non-standard location (eg: /usr/local/bin/gpg)
Fixed a typo in a variable name
Refactored file fetch and signature verification code

[CHG] Moved all "use" statements to the top of the file

[CHG] Refactored file fetch and signature verification code to be as
close to the original as posible while implemmenting required features.

[ADD] Added a new DBDefs option which defines how validation deals with
the missing signature file.
Passthrough GPG exit code on FAIL
Updated arguments to the system command

Split "--option value" parameter for the systems command into two
separate arguments.
Add constraints to ensure the right domains are picked for some rels
Adding autoselect + validation for IMDb samples stuff
Ensure the right level of SecondHandSongs is used
Standardising the way release events are shown
Add some info to meta for releases
Adding meta to labels and works
Add more info to work and release
Add begin/end area
Add area to wikidata and wikipedia autoselect
Merge branch 'beta' of https://bitbucket.org/metabrainz/musicbrainz-server into mbs-6203
Expanding this for wikipedia/areas
Adding alphabetical order