Improvements to long-read-giraffe experiments parameter search pipeline

[ellwi]

Snakefile

• fixed filenames in length_by _mapping
• fixed locale errors in join and sort commands throughout
• changed memory request on speed_from_log and memory_from_log

parameter_search.py

• added options to sample parameters from lognormal or truncated normal distributions
• added option to include a "mean" value in parameter_search_config
• added option to run benchmarks of default and mean parameter sets