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.
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.
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 new names for get_memory parameters
Use physmem and realmem from get_memory() in the appropriate places
Merge pull request #785 from phil-davis/master

Tidy up use of hw.physmem and hw.realmem from get_memory()
Increased needed memory for APC to 512M + code cleanup

- Increased the needed memory for APC to 512M as we often run into memory problems on our 256M box
- fixed the RAM calculation to divide by 1024 and not 1000
- code cleanup (renaming variables and creating new to avoid magic numbers)
Provide get_uptime_sec in a common include file

so it is available to anything that cares.
Call get_uptime_sec from functions.inc.php

to avoid code duplication
Use ipprotocol to check gateway protocol, this fix a issue that allow to set more than one default gateway when it's dynamic
Show a count of the CPUs if more than one is detected, and show how those CPUs are supplied by the hardware.
Merge pull request #787 from phil-davis/master

Provide get_uptime_sec in a common include file
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/
Merge pull request #788 from jean-m-cyr/master

Dummynet does not require burst size specification
Fix #3172, return_gateway_groups_array() was returning the last vip since it was using wrong variable name on iteration
shaper burst may be blank, but if not then must be numeric
Merge pull request #789 from jean-m-cyr/master

shaper burst may be blank, but if not then must be numeric
Fix #3174 Handling of gateway groups in openvpn_restart()
If the underlying vip of a gateway group that an openvpn client is bound
to is in backup mode then the client should not start.
touch up text, s/nat/NAT/
fix text