- Change project to C# 8

- Support NullableAttribute
- Improve IList performance
- Fix mapping to existing struct

package: add netstandard 2.0

feature: support code generation
feature: 2 ways mapping
feature: unflattening
feature: map to constructor
feature: map by properties path
feature: max depth
feature: add before mapping

fix: Compile using ForDestinationType

fix: include non-public member
fix: EF not support Expression.Default

fix: map to target from null value should return null

- minor performance improvement

- improve script readability
- support ExpressionDebugger

feature: support IDictionary
fix: ignore index properties for auto ma…

…pping

fix mapping from static property throw NullReferenceException

- allow map to target without default constructor (sp thx to Burgyn)

- throw when pass nest destination member access to Map method

fix MapsterMapper#118 mapping enum to poco

fix nullable enum mapping