Add Materials From G-Code

It is possible to add new materials or edit existing materials by using "magic comments" in a G-Code file.

A full example is:

(o=1, nu=2, na=5mm Mild Steel 40A, ph=3.1, pd=0.1, ch=0.75, fr=3000, kw=0.5, th=1, ca=45, cv=110, pe=0.1, gp=5, cm=1, jh=0, jd=0)

This is made up of the following mandatory parameters:
Name Description
o=    option
nu=   material number (see note below)
na=   material name (see note below)
ph=   pierce height
pd=   pierce delay
ch=   cut height
fr=   feed rate

Plus the following optional parameters:
Name  Description
kw=   kerf width
th=   thc enable (0=disable, 1=enable)
ca=   cut amps
cv=   cut voltage
pe=   pause at end delay
gp=   gas pressure (Powermax)
cm=   cut mode (Powermax)
jh=   puddle jump height
jd=   puddle jump delay

The options are:
Option  Description
0       Create a temporary default material
        This will be discarded by a manual reload or a LinuxCNC restart
1       Add a new material if it does not exist
2       Overwrite an existing material if it exists
        Add a new material if it does not exist

Formatting rules are:
. The entire comment must be in parentheses
. The beginning of the magic comment must be (o=
. The equals sign must immediately follow each parameter with no space
. The above mandatory parameters must be in the magic comment (see note below)
. There can be any number and type of magic comments in a G-Code file with the exception of option 0. If more than one option 0 are in the G-Code file then only the first one found will be used and the others will have an error reported

NOTE: nu and na are not required for option 0.