Nightly build pipeline

[frank-dong-ms-zz]

new nightly build pipeline:

1. add new nightly build pipeline project, disable project build from solution
2. add NuGet package version updater project
3. add new Azure nightly build pipeline and template file
4. TestFrameworkCommon project use conditional reference to source code:
   a. when reference from functional test, use project reference
   b. when reference from nightly build test, use package reference
5. process of nightly build pipeline:
   a. get latest NuGet package version from public NuGet feed
   b. update version to .props file
   c. build nightly build project
   d. run nightly build tests, which is functional test for now
   e. output test results
6. a sample test pipeline can be seems here: https://dev.azure.com/dnceng/public/_build?definitionId=644&_a=summary
7. have issue in Ubuntu platform, disable for now, will continue investigate and send out update later