pbr: update to 1.2.0-r2

pbr: update to 1.2.0-r2

Makefile:
* stop shipping/dealing with the firewall hotplug (obsolete)
* install a third user-script (dnsprefetch) by @betonmischer

Config:
* remove obsolete options
* include the new user script

Init-script:
* start much earlier so that on boot, the procd_add_raw_trigger works on all systems
* create a ubus() helper function so that service delete does not produce "Command not found"
* rename options to better reflect their function:
  * procd_lan_device to lan_device
  * procd_wan_interface to uplink_interface
  * procd_wan6_interface to uplink_interface6
  * procd_wan6_metric to uplink_interface6_metric
  * wan_ip_rules_priority to uplink_ip_rules_priority
  * wan_mark to uplink_mark
* visually separate run-time variables from variables loaded from config options
* use ${IPKG_INSTROOT} when sourcing files
* fix typo in str_to_dnsmasq_nftset()
* use pidof to kill dnsmasq in dnsmasq_kill()
* add helper function uci_add_list_if_new()
* add helper function uci_changes()
* add helper function ubus() so that service delete does not produce "Command not found"
* implement the dnsmasq features check similar to dnsmasq init script
* add get_url() function similar to luci package
* add/modify error and warning messages
* change how mktemp is used for more reliable file creation
* unset non-true boolean package config options on load for easier checks later
* improve handling of nft/nft set options
* fewer calls to resolver() and resolver() optimization to speed up the service
* use softlinks instead of duplicating dnsmasq nftset files into each instance
* prevent duplication of dnsmasq nftset elements
* option to target a specific dest dns port in DNS policies
* bugfix: more reliable interface reloads
* display README links to errors/warnings sections if any errors/warnings discovered

Uci-defaults:
* transition from old options to new ones

Signed-off-by: Stan Grishin <[email protected]>