Allow parametized views to be dynamic with optional parameters

Currently we have to construct views with static parameters if we want to reuse them across many filters e.g.

```
CREATE VIEW sold_by_duration AS
SELECT
duration,
count() AS value
FROM default.uk_price_paid
WHERE ((postcode1 = {_postcode:String}) OR (district = {_district:String}) OR (town = {_town:String}))
GROUP BY duration

SELECT *
FROM sold_by_duration(_postcode = 'SL4', _district = 'X', _town = 'X')
```

Proposal is to allow a column name to be passed e.g.

```
CREATE VIEW sold_by_duration AS
SELECT
duration,
count() AS value
FROM default.uk_price_paid
WHERE _column:Column = {_value:String}
GROUP BY duration

SELECT *
FROM sold_by_duration(_column = 'postcode1', _value = 'SL4')
```

Alternative and maybe complementary is to allow parameters to be optional - they will in turn be optimized away. This is more challenging obviously i.e.

```

SELECT *
FROM sold_by_duration(_postcode = 'SL4')

becomes

SELECT
duration,
count() AS value
FROM default.uk_price_paid
WHERE postcode1 = 'SL4'
GROUP BY duration

```