Improve ConfigNode load/save perf

[NathanKell]

Rewrite PreFormatConfig to iterate through strings less and to support skipping checking for {} and //
Also patch writing for a little bit of extra perf.

The preformat patch includes, disabled, siimav's parallel implementaiton; it's disabled because at the moment it's strictly slower than stock code AFAICT.

This yields up to an 8x boost (or so) in read/write performance for sfs, and lower but still substantial gains elsewhere.

For testing, add this to a file in gamedata and then load craft/saves.

@KSP_COMMUNITY_FIXES:FINAL
{
	@CONFIGNODE_PERF_SKIP_PROCESSING_KEYS
	{
		item = attPos0
	}
	@CONFIGNODE_PERF_SKIP_PROCESSING_SUBSTRINGS
	{
		item = attRot
	}
}

Note that the skip nodes will only apply after MM loads; before that you'll just get the regular speedup.