Add properties property for Template class

[Danieladu]

Fixes: #3273

Description

For some requirements from Composer side. Describe here:
Structure LG parsed result should cover the common key/value pairs results.

For example:

# template
[Activity
 Text=good
 Speak=hi
]

The parsed Template would contains a property named properties, in which would contains:

properties: {Text: "good", Speak:"hi", $type:'Activity'}

Particular cases

• Pure Expression reference would be ignore

[A
 key1=value1
 ${T2()}     -> this one would be ignored
]

• would keep the origin list info

[A
 list = a | b
]

the properties would be:
{list: ['a', 'b'], $type: 'A'}

[coveralls]

Pull Request Test Coverage Report for Build 547363540

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 2 unchanged lines in 2 files lost coverage.
• Overall coverage increased (+0.03%) to 84.901%

---

Files with Coverage Reduction	New Missed Lines	%
libraries/botbuilder-lg/src/templatesParser.ts	1	89.46%
libraries/botbuilder-lg/src/template.ts	1	75.0%

Totals
Change from base Build 546814253:	0.03%
Covered Lines:	18306
Relevant Lines:	20581

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💛 - Coveralls

[boydc2014]

Composer also need the type, ie, Activity, HeroCard, like that.

So, it would be good to have a $type property in that json