Query syntax: Add support for spaces in field names

At the moment fields can be registered statically or dynamically with spaces in them:

var index = new FullTextIndexBuilder<int>()
    .WithObjectTokenization<Customer>(o => o
      .WithId(c => c.CustomerId)
      .WithField("Customer Name", c=>c.Name)

But there’s no way using the LIFTI query syntax to filter on a field name with a space in it:

Customer Name=Something

The first part of the field name becomes part of the query.

We need to introduce something to quote a field name, e.g.

[Customer Name]=Something

We’d need to allow for edge cases where the field name contains a close bracket and it needs to be escaped.

[mikegoatly]

I’m going to split wildcards out to #77 - they add significant complexity and implementing this feature without them add its own value.

[h0lg]

It would also be be nice to match multiple fields against the same expression. Let’s assume I want to match the same query against the UTF8 and the ASCII representation of a customer name:

var index = new FullTextIndexBuilder<int>()
    .WithObjectTokenization<Customer>(o => o
      .WithId(c => c.CustomerId)
      .WithField("Customer Name", c => c.Name)
      .WithField("Customer ASCII Name", c => c.AsciiName)

If possible, I’d like a query without repetition, e.g. [Customer Name|Customer ASCII Name]=Something

Or let’s assume I want to search a group of dynamic fields sharing the same same prefix or suffix - then I’d like to query those with [prefix*]=query or [*suffix]=query.

Obviously, this can be worked around by OR-combining the same query for different field names - so it may really just a be a convenience feature for people manually writing LIFTI queries.