Update 'Get-ChangeLog' to make it more accurate
Use "||" as the delimiter instead of "|", so it works for commit message that has the pipeline operator in it.
Handle merges that create a merge node in history.
Do not treat powershell team members as external contributors.
Based on standard practices, we need to have a copyright and license notice at the top of each source file. Removed existing copyrights and updated/added copyright notices for .h, .cpp, .cs, .ps1, and .psm1 files.
Updated module manifests for consistency to have Author = "PowerShell" and Company = "Microsoft Corporation". Removed multiple line breaks.
Separate PR coming to update contribution document for new source files: #6140
Manually reviewed each change.
Fix#6073
Create the module 'releaseTools.psm1' under 'tools' folder, which expose the function 'Get-ChangeLog' to generate a release change log based on the local commit history.
