Add options for export streams

[mikee47]

This PR addresses issue #60 to enable variations in how JSON is generated.

An extensible ExportStream::Options structure has been added which can be manipulated via an export stream's getOption and setOption methods. This is cleaner than changing the method signatures for all createExportStream methods.

The Streaming test module demonstrates the effect of setting these options:

Streaming object export options (intarray)

RootStyle::content 13,28,39,40
RootStyle::braces [13,28,39,40]
RootStyle::name "int_array":[13,28,39,40]
RootStyle::object {"int_array":[13,28,39,40]}

With rootName override:

RootStyle::content 13,28,39,40
RootStyle::braces [13,28,39,40]
RootStyle::name "newname":[13,28,39,40]
RootStyle::object {"newname":[13,28,39,40]}

Streaming object export options (root)

RootStyle::content "int_array":[13,28,39,40],"string_array":["a","b","c"],"object_array":[],"color":"red","simple-bool":true,"simple-string":"donkey","simple-int":100,"simple-float":3.1415927
RootStyle::braces {"int_array":[13,28,39,40],"string_array":["a","b","c"],"object_array":[],"color":"red","simple-bool":true,"simple-string":"donkey","simple-int":100,"simple-float":3.1415927}
RootStyle::name {"int_array":[13,28,39,40],"string_array":["a","b","c"],"object_array":[],"color":"red","simple-bool":true,"simple-string":"donkey","simple-int":100,"simple-float":3.1415927}
RootStyle::object {"int_array":[13,28,39,40],"string_array":["a","b","c"],"object_array":[],"color":"red","simple-bool":true,"simple-string":"donkey","simple-int":100,"simple-float":3.1415927}
// With rootName override:
RootStyle::content "int_array":[13,28,39,40],"string_array":["a","b","c"],"object_array":[],"color":"red","simple-bool":true,"simple-string":"donkey","simple-int":100,"simple-float":3.1415927
RootStyle::braces {"int_array":[13,28,39,40],"string_array":["a","b","c"],"object_array":[],"color":"red","simple-bool":true,"simple-string":"donkey","simple-int":100,"simple-float":3.1415927}
RootStyle::name "newname":{"int_array":[13,28,39,40],"string_array":["a","b","c"],"object_array":[],"color":"red","simple-bool":true,"simple-string":"donkey","simple-int":100,"simple-float":3.1415927}
RootStyle::object {"newname":{"int_array":[13,28,39,40],"string_array":["a","b","c"],"object_array":[],"color":"red","simple-bool":true,"simple-string":"donkey","simple-int":100,"simple-float":3.1415927}}

[mikee47]

One downside of using setOptions, etc. on ExportStream is that they're inaccessible to immediate Format::exportToStream calls. It would also be nice to include the pretty setting so applications can do everything via the generic interfaces.

[mikee47]

Closing in favour of #68. This approach is too closely tied to the internal implementation using RootStyle, and the API is inconsistent.