Allow bracket pairs to share open tokens or close tokens

[DragWx]

This addresses issue #301. Initial testing allows the Verilog case and endcase tokens to match correctly, and doesn't seem to break any other files I opened.

This modification does three things:

1. Adds pairsWith to Token and everything that instantiates tokens.
2. When loading the textmate languages, braces are still only added once to the map, but pairsWith is now used to keep track of which open braces have been paired with which closing braces, to allow one-to-many associations.
3. In AddCloseBracket, the open brace checks its pairsWith list to determine if the close bracket should be a match, instead of checking for like keys.

[skrobchik]

#170 Could this be related?

[DragWx]

Without knowing the exact extension you're using for LaTeX support, I just searched the marketplace for one and found LaTeX Workshop. Inside LaTeX-Workshop/syntax/syntax.json are the following bracket definitions:

	"brackets": [
		["{", "}"],
		["[", "]"],
		["(", ")"],
		["\\left(", "\\right)"],
		["\\left(", "\\right."],
		["\\left.", "\\right)"],
		["\\left[", "\\right]"],
		["\\left[", "\\right."],
		["\\left.", "\\right]"],
		["\\left\\{", "\\right\\}"],
		["\\left\\{", "\\right."],
		["\\left.", "\\right\\}"],
		["\\left<", "\\right>"]
	],

Sure enough, there's some sharing going on between these tokens, so issue #170 is very likely to be related.