Update settings.py to resolve UncompressableFileError

The latest Horizon master requires xstatic.pkg.bootstrap_datepicker
library and an updated settings.py that imports it correctly,
otherwise there will be a fatal UncompressableFileError.
We need to reflect the latest horizon settings.py in dashboard

Change-Id: I3cd4b2a62b9df534ca55df4f4554b53d94f304cb
Closes-Bug: 1373048
Merge "Update settings.py to resolve UncompressableFileError"