Bump to Lmod/7.7.31-f4df153, change to opt-in for settarg & help some rpmlint warnings

[fgeorgatos]

bump to a latest and greatest Lmod version.

[fgeorgatos]

@plabrop :
only rpmlint warnings remaining are the following, which are kind of expected:

[fotis@demo2 bic]$ date;rpmlint -i *spec
Wed May  2 14:42:24 CEST 2018
Lmod-illumina.spec:62: W: unversioned-explicit-provides environment(modules)
The specfile contains an unversioned Provides: token, which will match all
older, equal, and newer versions of the provided thing.  This may cause update
problems and will make versioned dependencies, obsoletions and conflicts on
the provided thing useless -- make the Provides versioned if possible.

Lmod-illumina.spec: W: invalid-url Source1: Lmod-files-7.0.tar.gz
The value should be a valid, public HTTP, HTTPS, or FTP URL.

0 packages and 1 specfiles checked; 0 errors, 2 warnings.
[fotis@demo2 bic]$

@plabrop , @johnnydevaprasad: your review?!