Support Enum serialization

[wertzui]

Serialization of enums is currently not supported. It should be added and it should be configurable to serialize them either is int or as string.

[ddrinka]

Hi @wertzui, thanks for your great ideas.

This version of ApacheOrcDotNet is end-of-life in our internal utilization. A new ORC reader in C# will be getting added to this repository shortly, but the work to create a new writer hasn't been prioritized.

This current implementation spends a significant proportion of its time in garbage collection, leading to pretty poor performance. It needs to be reoriented into a column-first batched-array structure to make sense going forward.

I'd gladly accept pull requests for improvements, but unfortunately I won't be able to commit time to making the changes you've requested.

With regard to this request in particular, I've found that I am nearly never able to serialize an existing POCO directly to one of the big-data storage formats. I'm always creating a pass-through type that gets serialized and converted between the internal representation. I would suggest following the same approach here and in #13, creating types that precisely match your schema and converting data from your internal representation to those dedicated types.

[ddrinka]

I'll leave this open to represent a beneficial feature request, but just want to be upfront that I won't be able to make the changes requested in the near future.