Revert "Spaces, not tabs"

This reverts commit 9e1496b6bb8476bda3825854b5a4f4f8c0d26da3.
Support different log levels for different log destinations
Added overload for AddLogDestination that uses existing LogLevel
Added LogLevel::None
Added Passthru option

This is useful when piping output from another process that is also
using nst-log. The only formatting applied to the message is indent.
It will be broadcast to all log destinations.
Added notes on thread-safety
Corrected re-insertion of default log on SetLogLevel call
Added .gitignore
Fixed debug build