[phosphor-webui] Enable style-src 'unsafe-inline'

[Derick]

>  We would like to use angular-ui-grid module to support grid feature.

Using a system that inlines that code makes maintenance extremely
hard. Using inline styles creates specificity issues and is goes
against best practices. I am assuming you are referring to
http://ui-grid.info/? Like Ed, I would also like to understand the use
case and why that is needed.