Use expression-bodied members

[c0shea]

Replace code braces in properties with expression-bodied members in C# 6.

For example, this:

public static bool IsTraceEnabled
{
    get { return LogLevel.Trace >= LogLevel; }
}

becomes this:
public static bool IsTraceEnabled => LogLevel.Trace >= LogLevel;

[codecov]

Codecov Report

Merging #2361 into master will decrease coverage by <1%.
The diff coverage is 65%.

@@           Coverage Diff           @@
##           master   #2361    +/-   ##
=======================================
- Coverage      82%     82%   -<1%     
=======================================
  Files         318     318            
  Lines       22791   22768    -23     
  Branches     2783    2783            
=======================================
- Hits        18690   18657    -33     
- Misses       3399    3408     +9     
- Partials      702     703     +1

[304NotModified]

thanks again!