ElapsedBuildTime is now aware of the current culture, variables renamed, newline adaptions, c# 6/7

[Barokai]

ElapsedBuildTime is now aware of the current culture, Some variables renamed in BuildEvents.cs, replaced \r\n with Environment.NewLine

Introduced some c# 6/7 language features:

• c# 6 expression-bodied members for get-only indexers
• c# 6 expression-bodied members for get-only properties
• c# 7 expression-bodied members for ctors
• c# 7 expression-bodied members for get accessors
• c# 7 out variable in method invocation

[mike-ward]

Cleans things up a bit. Thanks!

[Barokai]

you're welcome, thanks a lot for merging my PR :)