2018.09.16: Expect delayed nightly Slicer installers and extensions

Similarly to the other day [1], we are finalizing work related to an other project and are using the Slicer build infrastructure.

This means the Slicer packages and associated extensions will be available later today or only tomorrow.

Thanks for your patience,

[1] 2018.09.13: Only nightly Slicer packages - do not expect extensions this morning