Emit declaration files, filtering out internals

[huafu]

Closes #745

FYI reviewers all changes are about adding the @internal comment and changing the tsconfig so that declaration files are emitted.
Some files look like more changes, but it's just some re-ordering of methods depending on their modifiers which has been done automatically by the linter. Some other changes might be the refactoring from export {...} to individual exports as the @internal does not work within export maps.

[coveralls]

Pull Request Test Coverage Report for Build 1881

• 22 of 22 (100.0%) changed or added relevant lines in 4 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.04%) to 90.732%

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Totals
Change from base Build 1879:	-0.04%
Covered Lines:	966
Relevant Lines:	1015

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💛 - Coveralls

[huafu]

Weird, why overages decreased since there was no code change? could the extraction of export {...} into single exports do that?