Backport explicit Property Names such as @Excepetion

[warrenbuckley]

This is to support porting over from Serilog.Filters.Expressions that supported more verbose/explicit names
Fixes #63

@Message
@MessageTemplate
@Level
@Exception
@TimeStamp
@Properties

Note: I have not added more verbose names for Renderings and EventId as these were not present in Serilog.Filters.Expressions.
So I will leave it up to you @nblumhardt if you want to add or support them as well.

[warrenbuckley]

Here is my related PR of me porting across from Serilog.Filters.Expressions
Be super cool of you @nblumhardt if you were able to look over these changes to see if there is anythign I have missed or perhaps done wrong.

warrenbuckley/Compact-Log-Format-Viewer#469

[nblumhardt]

Thanks for the PR, @warrenbuckley!

I had in mind that we'd implement this through NameResolver, rather than add support directly. I'll take a look later today and see if I can come up with a way to do it, and loop back here :-)

I checked out your PR in Compact-Log-Format-Viewer, LGTM.

[warrenbuckley]

Hi @nblumhardt
Yes let me know how I should intend to use NameResolver to map properties as needed.

[warrenbuckley]

Closing this PR and using PR #65 for discussion