making activate.bat relocatable (windows)

[kbrowder]

set VIRTUAL_ENV=somepath

could be changed to
set VIRTUAL_ENV=%~dp0..

and then the virtual env would be relocatable on windows with the exception of exe script wrappers.

[felciano]

Would be great to get this fixed -- seems like it would solve davidmarble/virtualenvwrapper-win#21 as well.

[techtonik]

+1

[arizvisa]

Adding a reference to the newest issue #1067 related to this to help consolidate efforts on solving this half-decade old problem.

[tobiasherp]

+1

[arizvisa]

@tobiasherp, please +1 in issue #1067. You can also use the "reaction" icon instead of a comment to show relevance.