Create config utils module for managing common functions in config

[jerdra]

Some groovy code snippets are duplicated across config files. For example the snippet:

Closure get_partition;
if (partition instanceof Closure){
    get_partition = partition
}else{
    get_partition = { t -> partition }
}

Closure cacheDir;
if (params.cache_dir){
    cacheDir = { f ->
                    def d = new File("$params.cache_dir/$f")
                    d.mkdirs()
                    "$params.cache_dir/$f"
               }
}else{
    cacheDir = { f -> "" }
}

Is re-used in multiple config files. Originally thought to define all config specs in the main boonstim.nf.config file but the scope induced by includeConfig doesn't seem to carry over function definitions - they are local.

The solution here would be to create a groovy script containing function definitions that can be imported in each of the config files.