[PORT][LG] Robust Template CRUD with Two-phase parsing of LG

[Danieladu]

Close: #2062
Use two-phase to parse the LG content.
The first phase just split the templates and get a clear template division.
Second phase parse template body with more elaborate rules.

• Advantage:
  The division of the template does not depend on some internal errors in a template, making the division of the template more robust, which makes the CRUD of the template more friendly.
• Disadvantage:
  [Engineering]It will be more difficult to merge the two-phase diagnostics.

new features:
Import and Option definition should in front of templates.
so,

# template
- hi

[import](a.lg)  -> invalid
> !# @strict = true -> invalid

[import](a.lg)  -> valid
> !# @strict = true -> valid

# template
- hi

[coveralls]

Pull Request Test Coverage Report for Build 122755

• 191 of 220 (86.82%) changed or added relevant lines in 14 files are covered.
• 11 unchanged lines in 4 files lost coverage.
• Overall coverage increased (+0.02%) to 77.446%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
libraries/botbuilder-lg/src/sourceRange.ts	11	12	91.67%
libraries/botbuilder-lg/src/templateExtensions.ts	9	10	90.0%
libraries/botbuilder-lg/src/evaluator.ts	3	5	60.0%
libraries/botbuilder-lg/src/expander.ts	3	5	60.0%
libraries/botbuilder-lg/src/staticChecker.ts	18	20	90.0%
libraries/botbuilder-lg/src/templatesParser.ts	117	126	92.86%
libraries/botbuilder-lg/src/extractor.ts	1	13	7.69%

Files with Coverage Reduction	New Missed Lines	%
libraries/botbuilder-lg/src/analyzer.ts	1	93.75%
libraries/botbuilder-lg/src/staticChecker.ts	1	95.97%
libraries/botframework-streaming/src/webSocket/webSocketTransport.ts	2	80.65%
libraries/botframework-streaming/src/webSocket/webSocketServer.ts	7	66.67%

Totals
Change from base Build 122742:	0.02%
Covered Lines:	11879
Relevant Lines:	14618

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💛 - Coveralls