Make GGIR run easier on machines not configured for UK/US

[vincentvanhees]

This PR:

• Adds parameters dec_reports and dec_config to complement sep_reports and sep_config that already existed. I have tested this on Dutch configured laptop and it now works smoothly, fixes sep_report and sep_config not sufficient for working with non-UK/US configured machines? #1048.
• While doing this I also tidied up the way params_output is passed on to some of the functions.
• Adds Sys.setlocale("LC_TIME", "C") in a more systematic way. For part 2 and 5 it turned out to be necessary to also set this inside the functions that are run in parallel, because somehow R does not pass on this setting to the parallel process, fixes Part 2 report stores some day names in local languages #1047.
• I observed that parameter week_weekend_aggregate.part5 was not used, I have now made sure it is actually used.
• Parameters sep_reports and sep_config, were not checked for being a character by check_params, now also fixed.

Checklist before merging:

• Existing tests still work (check by running the test suite, e.g. from RStudio).
• Added tests (if you added functionality) or fixed existing test (if you fixed a bug).
• Updated or expanded the documentation.
• Updated release notes in inst/NEWS.Rd with a user-readable summary. Please, include references to relevant issues or PR discussions.
• Added your name to the contributors lists in the DESCRIPTION file, if you think you made a significant contribution.

[vincentvanhees]

@jhmigueles I tested this on a Dutch laptop and have now asked the group in Paris to test it on their computer. However, maybe you want to inform the group you developed the sep_reports argument for to start using these new dec_* parameters and ask them to test it to?

@l-k- Previously I was setting LC_time to C in every specific instance of GGIR code where language is important, with this PR I am attempting to set it more broadly such that we do not always have to worry about language issues. May I ask you to have a look at how I now enforce LC_time. More specifically, I am not sure how to pass on system settings via foreach, so I decided to re-enforce it also inside the subfunctions main_part2 and main_part5 inside g.part2 and g.part5. Does this make sense to you or can you see a more elegant way to do this?

[l-k-]

looks good!

[l-k-]

nice! Maybe part 6 too? Or can this definitely never apply to part 6?

[vincentvanhees]

Yes, but I have now committed that to a different open PR which comes with many other updates to part6, in that way I the merge will go easier 16b97f0