Populate extra exception properties

[niemyjski]

We should be looking at the exception object and storing any extra properties for example for the error object looks like this:

{
    "stack": "xyz",
    "message": "test",
    "extraproperty": "test"
}

We should be storing extraproperty as an object in extended data as shown here: https://github.com/exceptionless/Exceptionless.Net/search?utf8=✓&q=extra We might need to create an exception that has this in c# and look at the json that is created so we ensure the added dictionary is correct for deserialization..

NOTE: There are known exception properties that should be ignored: https://github.com/csnover/TraceKit/blob/master/spec/fixtures/captured-errors.js

[niemyjski]

@frankebersoll I've updated the description.