oe-git-proxy: Add a new comprehensive git proxy script

oe-git-proxy: Add a new comprehensive git proxy script

oe-git-proxy.sh is a simple tool to be used via GIT_PROXY_COMMAND. It
uses BSD netcat to make SOCKS5 or HTTPS proxy connections. It uses
ALL_PROXY to determine the proxy server, protocol, and port. It uses
NO_PROXY to skip using the proxy for a comma delimited list of hosts,
host globs (*.example.com), IPs, or CIDR masks (192.168.1.0/24). It is
known to work with both bash and dash shells.

V2: Implement recommendations by Enrico Scholz:
    o Use exec for the nc calls
    o Use "$@" instead of $* to avoid quoting issues inherent with $*
    o Use bash explicitly and simplify some of the string manipulations
    Also:
    o Drop the .sh in the name per Otavio Salvador
    o Remove a stray debug statement

V3: Implement recommendations by Otavio Salvador
    o GPL license blurb
    o Fix minor typo in comment block

Signed-off-by: Darren Hart <dvhart@linux.intel.com>
Cc: Enrico Scholz <enrico.scholz@sigma-chemnitz.de>
Cc: Otavio Salvador <otavio@ossystems.com.br>
git-proxy cleanup

Signed-off-by: Darren Hart <dvhart@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>