First checklist item from #125 - remove `dynamic`

Nullable type destructuring can be achieved without using `dynamic` - this change makes it possible to destructure `Nullable<T>` as scalar values on iOS.
Merge pull request #335 from nblumhardt/dev

First checklist item from #125 - remove `dynamic`
Changed to use stream for HTTP in Splunk
Merge pull request #336 from merbla/splunkstream

Changed to use stream for HTTP in Splunk (#215)
Added optional Encoding parameter to RollingFileSink and FileSink constructors.
Merge branch 'master' of https://github.com/object/serilog into object-master
Merge branch 'object-master' into dev
Changelist