Able to add any extension as a CLI pattern

[chrimc62]

This allows adding .uischema files and other extensions to better support testing and ad hoc use.
Checked-in generated C# support files even though projects are just for
testing.

[codecov-commenter]

Codecov Report

Merging #903 into master will increase coverage by 0.48%.
The diff coverage is 77.77%.

@@            Coverage Diff             @@
##           master     #903      +/-   ##
==========================================
+ Coverage   58.47%   58.95%   +0.48%     
==========================================
  Files         217      218       +1     
  Lines       15313    15846     +533     
  Branches     2102     2148      +46     
==========================================
+ Hits         8954     9342     +388     
- Misses       5812     5921     +109     
- Partials      547      583      +36     

Impacted Files	Coverage Δ
packages/dialog/src/library/schemaMerger.ts	79.40% <77.77%> (ø)
...kages/luis/src/commands/luis/application/create.ts	60.00% <0.00%> (-24.22%)	⬇️
...rc/commands/luis/application/assignazureaccount.ts	80.00% <0.00%> (-20.00%)	⬇️
...kages/qnamaker/src/commands/qnamaker/kb/publish.ts	85.71% <0.00%> (-14.29%)	⬇️
...ages/luis/src/commands/luis/application/publish.ts	85.71% <0.00%> (-14.29%)	⬇️
...aker/src/commands/qnamaker/endpointkeys/refresh.ts	85.71% <0.00%> (-14.29%)	⬇️
...ematics/mathematics_helper/AppMathematicsHelper.ts	85.71% <0.00%> (-14.29%)	⬇️
...atics/confusion_matrix/AppBinaryConfusionMatrix.ts	85.71% <0.00%> (-14.29%)	⬇️
packages/luis/src/commands/luis/train/show.ts	89.47% <0.00%> (-10.53%)	⬇️
...ackages/luis/src/commands/luis/application/show.ts	89.47% <0.00%> (-10.53%)	⬇️
... and 53 more

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[munozemilio]

Is this intended?