Allow double underscore in the field name for filtering

[gobimcp]

In some cases, we will need to allow field names with double underscores in it while filtering. So PR updates the newer version of the method parseUriParams which allows double underscores in the field names without breaking existing usages.

One case where this new logic will have issue is when we use implicit eq filter with a double underscore field such as foo__bar=value and in this case we might need to use the explicit eq (foo__bar__eq=value) to make this work, otherwise it will consider bar as filter and throw invalid filter exception.

[gobimcp]

Thanks @boulter. Can you please merge this as well?