Misleading comments in edknrc_template.egsinp input file

[dworogers]

Describe the bug

edknrc_template.egsinp describes source options as

SOURCE NUMBER= 0 # 0,1,2
                 # 0: point source AT origin,   emission along Z-axis
                 # 1: point source AT origin,   isotropically radiating in 4Pi
                 # 2: point source NEAR origin, emission along Z-axis

whereas the manual description is much more precise and less misleading

SOURCE NUMBER 0|1|2
0 ==> Photon moving along Z axis forced to interact at origin
1 ==> Point source at origin, isotropically radiating into 4 Pi
2 ==> Same as 0 but interaction point as in old code

Given that sources 0 and 2 are VERY different from 1, I think their misleading descriptions in the template file should be made the same as the manual.

[ftessier]

@dworogers here is the update, I simply copied what was in the manual to the .egsinp template:
https://github.com/nrc-cnrc/EGSnrc/pull/1130/files