make uninstall

[Alex Merry]

On Friday 30 January 2015 10:44:23 Alex Merry wrote:
> Over on kde-frameworks-devel, there have been several requests to bring back
> `make uninstall` for KF5 and KF5-based projects.
> 
> KDELibs4 used to define this for any dependent projects (it's essentially
> `xargs rm < install_manifest.txt` under the hood), and we could easily add
> it to KDECMakeSettings (with an option to disable it).

We could also easily make it opt-in, either by making a separate module to 
define an uninstall target or by requiring projects or users to set a 
variable/option.

Alex