[PORT]Extend 'getProperty' builtin function to support accessing top memory

[Danieladu]

issue link: microsoft/botbuilder-dotnet#4029
Fixes #2448

Originally, getProperty accepts two parameters, the first parameter is an instance, and the second parameter is the property name which user wants to access the value from. In this mode, the user can not access the top-level memory from dynamic/special string property.

After this change, getProperty accepts only one parameter, that presents the root property from the memory.

Example:
Scope is :

{
"a:b": "value"
}

getProperty('a:b') would get string "value",

[coveralls]

Pull Request Test Coverage Report for Build 142036

• 9 of 9 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.006%) to 81.026%

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Totals
Change from base Build 142026:	0.006%
Covered Lines:	12965
Relevant Lines:	15283

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💛 - Coveralls

[chrimc62]