Bugfix in LargeSigmaHandler and expand vasp_gam auto checks

[esoteric-ephemera]

Two major changes:

• Since LargeSigmaHandler is a monitor handler (checks while output is still being written), it can occasionally misfire when parsing data from OUTCAR. This adds a fix to prevent jobs from being terminated when the handler itself fails to interpret partial file output
• Close #348 by expanding the scope of k-point checks to include KSPACING, and to also check for grid shifts in KPOINTS

[naik-aakash]

Thanks @esoteric-ephemera , was about to start working on adding the vasp gamma runs support when using KSPACING. Seems already in place 😃