rapidgator (download): avoid pipe, fix error 141 (SIGPIPE)

Appears on some devices (like Raspberry Pi).
plowdown: add new module download variable MODULE_xxx_DOWNLOAD_FINAL_LINK_NEEDS_EXTRA

Array variable containing curl's additionnal switches used on final link download (by plowdown).
core.sh (parse): standalone version (no more "|head -n1")

Rewrite to avoid potential SIGPIPE errors. Code is similar to parse_all() except for sed expressions.
filepup.net: initial module with download & probe support

Requires commit:
plowdown: add new module download variable MODULE_xxx_DOWNLOAD_FINAL_LINK_NEEDS_EXTRA
revision 1cd7c9127c5fa03b2345cce871d87ecedb5557cf
netload.in (download): get filename from official API

This was already the case for plowprobe.
core.sh (parse_attr, parse_all_attr): strict quoting pairing in sed expression
core.sh: add sha1() plowshare api
filepup_net (download): add missing uri_encode
filepup_net (download): translate /info/ to /files/ in link
sendspace (download, upload): enable -a/--auth module option.

Work both on user & premium account.
Notice that an official API is now available. Plowshare do not use it for now.