support specifying setenv statements to be added to module file, in easyconfig

[boegel]

(old internal ticket 223)

We should support specifying the setting of environment variables in module files, in the easyconfig.

For example:

moduleVars = {'EXTRA_VARIABLE':'some value'}

[fgeorgatos]

This issues may or may not be related to:
allowing for setting up generic modulefile lines ( eg I sometimes we need to set up aliases).

I think it would be relatively convenient to be able to add arbitrary items like
moduleLines = {'set-alias eb "time eb --robot $root/easybuild/easyconfigs --strict=ignore"'}
There are many use-cases for both variables, aliases and maybe we think of more.

[boegel]

Fixed, supported via modextravars easyconfig parameter.