Clean up how N_grid=1 bug in some EASE *.til files is addressed

[gmao-rreichle]

There is a bug in some EASE *.til files through at least Icarus-NLv4.

Affected files state "N_grid=1" in line 2 of the header, but the header still includes three additional lines for a second grid.
This is confusing and results in problems when the *.til files are read using canonical MAPL tools.

There is currently not a consistent approach in GEOSldas to work around this bug in preprocess_ldas_routines.F90.

Comments that identify the relevant lines were added as part of pull request #283.
(Search for "N_grid=1" in preprocess_ldas_routines.F90.)

One of the approaches consists of writing a corrected *.til file (subroutine correctEase()). This requires I/O and storage of large ASCII files, which ideally could be avoided, but it's not clear if that's possible.

It would be good to clean up and implement a single, consistent work-around for the bug.

cc: @biljanaorescanin