Parse new DeclarationReference format in TSDoc

[rbuckton]

This builds on #324 to support parsing the new DeclarationReference format in TSDoc.

[octogonz]

@rbuckton Thanks for contributing this PR! I apologize I haven't had a chance to look at it yet. I've been very busy the past week, but I should have some time on Friday.

[Gerrit0]

One concern I have:

This new form of declaration references appears to be incapable of supporting the {@label} tag.

tsdoc/tsdoc/src/beta/DeclarationReference.grammarkdown

Lines 157 to 161 in b7bddc1

	Meaning:
	`:` MeaningKeyword // Indicates the meaning of a symbol (i.e. ':class')
	`:` MeaningKeyword `(` DecimalDigits `)` // Indicates an overloaded meaning (i.e. ':function(1)')
	`:` `(` DecimalDigits `)` // Shorthand for an overloaded meaning (i.e. `:(1)`)
	`:` DecimalDigits // Shorthand for an overloaded meaning (i.e. ':1')