Cannot define the `now` option via the UI because of the `v` option

This one is a tricky bug, it seems that since the UI defines the `v` option in terms of the `now` option it creates a dependency conflict within the script if a user tries to set the `now` option themselves.

To reproduce add this to a Flux script in the UI:

```
option now = () => 2012-12-20

```

An error about option dependency will occur
```
option dependency: option "v" depends on option "now" defined in the same package at 0:0-0:0
```

We should investigate if the dependency issue is a real concern, or if we can redefine the `v` option in terms of something else instead of the `now` option.

Start by reproducing the issue in the UI with the provided Flux script and inspect how the UI defines the `v` option in relation to `now`. Determine whether the dependency conflict is required, then verify that users can define `now` without an option-dependency error.

Written by the indexing model from the issue text.