pfSense

shaper burst may be blank, but if not then must be numeric

Fix #3172, return_gateway_groups_array() was returning the last vip since it was using wrong variable name on iteration

Dummynet does not require burst size specification

Dummynet traffic shaper does not require burst size specification and
assumes 0 if not specified. Allow user to leave burst field blank/

Provide get_uptime_sec in a common include file

so it is available to anything that cares.

Use physmem and realmem from get_memory() in the appropriate places

Use new names for get_memory parameters

Use hw.physmem when calculating pfsense_default_state_size

hw.physmem is the actual amount of memory that FreeBSD/pfSense can get its hands on, so use this for the calculation.

Use updated get_memory var names

The value of minimum_ram_warning is designed to be compared to hw.physmem - so do that. Usse the appropriate physmem or realmem value in each place.

Improve var names in get_memory

realmem is the amount of actual (real) memory installed - the size of the RAM card - e.g. 256MB
physmem is the amount of memory available to FreeBSD after BIOS, video... has stolen some of realmem.
The variable names currently used are not very helpful for code readability. This standardises them. No functional change here.

s/require/require_once/g for filter.inc to avoid redeclaration errors in some rare cases.