the RangeEnabled option now has no effect, but it still exists in the API. A few
tests still use it to ensure this. This would only be considered a breaking
change if someone was relying on Pilosa to enforce the RangeEnabled: false
option to prevent fields being created in certain frames. This seems unlikely.
This PR adds the ability to import field values into RangeEnabled frames
using the `pilosa import` command.
Example:
```
pilosa import -i i -f f --field foo sample-vals.csv
```
imports data from sample-vals.csv, which contains data in the format:
```
[ColumnID, Value]
```
Also fixes a bug where `frame.rangeEnabled` was not being set on frame creation.
