pfSense

Remove unnecessary variable

Remove more cases of hard coded pfSense and use product_name

Introduce read_global_var:

- Add a new script, read_global_var, that returns the value of any item
contained in global array $g
- Replace all grep and sed magic from shell scripts

Introduce read_xml_tag.sh

Create /usr/local/sbin/read_xml_tag.sh, that will read a xml tag from
config file using xmllint. Replace all direct read using cat, grep, sed,
... by this script

pkg 1.6.x upgrade command called with -q is now respecting it

Do not run pkg update between first and second step of upgrade process

Remove old references to undefined variable firmwarelock

Call exit after detect another instance is already running, otherwise it would end up deleting pid file

Detect when pkg must be upgraded and do it early, followed by a pkg update to make sure metadata is updated

Cleanup cache and stale packages after install/delete