Adding some notes to the files for version management of downstream…

[Tobias-B-Besemer]

…projects

Added some notes to files lately changed (2019) that downstream projects (projects that use NsisMultiUser) can better manage & handle the versions of NsMultiUser (files).

Changes made:

• Added header with project name copied from Include\NsisMultiUser.nsh
• Copyright year bumped to 2019 in the header
• Added relative path (in the project) & file name to the header
• Added "Version" with last commit of file to the header

[Tobias-B-Besemer]

Note: Issue to add version info to stdutils, too: https://github.com/lordmulder/stdutils/issues/25