Add generic parser for mac address lists

This change generalizes the code used for parsing the configuration option
'p2p_client_list' and makes it suitable to use it in other contexts.
Add network specific AP black- & whitelists

This change allows the configuration options "bssid_whitelist" and
"bssid_blacklist" to limit the AP selection of a network to a specified
(finite) set or discard certain APs.

This can be useful for environments where multiple networks operate using the
same ESSID and where roaming between those is not desired.

It is also useful to ignore a faulty or otherwise unwanted AP.
Enable wildcards (*) in BSSID lists

In many context it seems suitable not just to enumerate a group of mac
addresses, but to use wildcards (ca:ff:ee:*:*:*).

This change expands the data structures used by mac lists to include a mask
indicating the significant (non-masked) portions of an address.