Add actor based "static" logging

[hseeberger]

Static means that the log level is fixed at compile time and hence the macros can just elide the logging code for too low levels.

[ludovicc]

Zero-log (http://code.google.com/p/zero-log/) uses @elidable to remove all unnecessary log statements at compile time. This is great if you want to ship a production level application with maximum performance, yet developers can still output debug statements on their machines.

[hseeberger]

Yeah, looks awesome.

[analytically]

+1 for @elidable support!

[PhilAndrew]

+1 for @elidable

[analytically]

The elide-below switch is a compiler switch, removing methods at compilation time. Thus this issue is invalid.