Provide Setting for defined or fallback proxy

[hastmu]

As there may be the need to define how to find the proxy, this is for just defining it, the check would proof that it works.

maybe something like:
/etc/apt-proxy-detect.conf

with
PROXY_RESOLVE=set,avahi,....
PROXY_SET=,...

[hastmu]

• Define file location
• Provide SET way of doing

[hastmu]

So location with the cache location
Setting it like

<cmd> set_default <proxy1>,<proxy2>

[hastmu]

default location is /usr/local/etc/apt-proxy-detect.bash

[hastmu]

one can set-default proxies with
$0 set-default ...

one can show defaults with
$0 defaults

[hastmu]

implementation done.