Add possibility to pass cluster params

[Karel Břinda]

This is how it was done for MOF-Search:

ifeq ($(SMK_CLUSTER_ARGS),)
    # configure local run
    SMK_PARAMS=--cores ${THREADS} --rerun-incomplete --printshellcmds --keep-going --use-conda --resources max_download_threads=$(MAX_DOWNLOAD_THREADS) max_io_heavy_threads=$(MAX_IO_HEAVY_THREADS) max_ram_mb=$(MAX_RAM_MB)
else
    # configure cluster run
    SMK_PARAMS=--cores all --rerun-incomplete --printshellcmds --keep-going --use-conda --resources max_download_threads=10000000 max_io_heavy_threads=10000000 max_ram_mb=1000000000 $(SMK_CLUSTER_ARGS)
endif