luci-app-lldpd: helpers for location data in lldpd

luci-app-lldpd: helpers for location data in lldpd

They should help with handling coordinate, address and ELIN formats.

It disassembles any lldp_location and fills corresponding fields. The
address fields used are globally common and include those used in Cisco
products. (lldpd has more address properties available)

Changes made to any field trigger write_lldp_location to compose a new
string saved to lldp_location.

The user can override everything by entering a raw config string (in
case an address type field is not available). The last field changed,
wins.

Signed-off-by: Paul Donald <newtwen+github@gmail.com>