Class representation for all parts that change between SQL drivers

[g105b]

We already have the Condition classes tracked in their own issue, because they have some useful functionality when combining different logical conditions, but this issue covers all the other parts of a query that might be output in a different way between different database drivers.

For example:

• like comparison uses slightly different syntax in MySQL to SQLite and Postgres (field like 'gr?g' in MySQL vs. field like 'gr_g' in others)

// TODO: More examples to flesh out the syntactical differences between the major vendors.