Change string to "Maximum new connections per host / per second(s)"

Clarifying the setting's meaning.

As suggested by forum member "Senser" on
https://forum.pfsense.org/index.php/topic,65472.msg356024.html#msg356024
Merge pull request #913 from Aeyoun/string-max-connections-per-host-per-second

Change string to "Maximum new connections per host / per second(s)"
Abort installation when pbi_add fails
Add https to update URLs and replace RELENG_8_3 by RELENG_10_0
Respect g['tmp_path']
Fix #2952, escape necessary chars to avoid xss injection
Add a mechanism by which the serial port can be forced on always regardless of the config setting. (useful for nano+vga setups)
Add a knob to let the user select which console (video or serial) is preferred in cases where there are multiple consoles present. Also provide a way to force this preference.