R function: combine_bgc_output

[GabrieleNocchi]

This function assumes that the lnl output suffix includes "LnL" but using the docker image the output in the suffix has "lnl" (lowercase).
Workaround: rename the output files changing the lnl to LnL

example:
bgc produces: test_stat_lnl_1
change it to: test_stat_LnL_1

[btmartin721]

Sorry for the confusion there. I'll add this to my list of things to fix too.

[GabrieleNocchi]

No problem, great job doing this! BGC all works. I haven't tested the introgress part though! Will probably do at some point!