Add SALT encoding and decoding

[BurnySc2]

Insert it here:

sc2-planner/src/constants/helper.js

Lines 182 to 188 in f806961

	const encodeSALT = (buildOrder) => {
	// TODO Encode salt build order
	return "Some salt build order encoded"
	}
	const decodeSALT = (saltEncoding) => {
	// TODO Decode salt build order from string

Use file /constants/salt_constants.js

References:
https://drive.google.com/file/d/0Bzrw_bC8iBjfSzFRRGlWWnNWNDg/view
https://github.com/Veritasimo/sc2-scrapbook/blob/68028fdbc7ce67a394ba139746e82485ebbf4312/SALT.cs#L150
https://www.reddit.com/r/starcraft/comments/25losh/build_order_tool_salt_update/chin15d/

Edit: Alternatively it could be done parsing the text of the spawningtool build order output by https://github.com/StoicLoofah/spawningtool

[BurnySc2]

Closing in favor of issue #9
SALT encoding does contain less information than sc2-planner build orders - technically it could be exported as SALT encoding, but that seems a lot of work for now.
Importing from SALT encoding will lack information, so that would be fairly pointless.

Importing from replays would provide complete information.