Parsing additional query parameters

In addition to the `config` parameter, would it be possible to add functionality to parse positional data from the query string?

```
&uid=
&view_uid=
&assembly=
&chr1=
&start1=
&end1=
&chr2=
&start2=
&end2=
```

Perhaps some parameters are optional:

The `assembly` key (`hg38`, etc.) would be used to look up chromosome sizes, to map coordinates to higlass space. If this key is not specified, it would be extracted from the default or specified viewconf.

If `uid` is not specified, it may be useful to extract the default viewconf for the first `view_uid` key. Or, if `uid` is specified and `view_uid` is not, parse the viewconf for the first key in its view ID array.

If `chr2`/`start2`/`stop2` are not specified, then they could be copied from `chr1`/`start1`/`stop1`.