Replaces named params with positional params
Adds open/close brackets via underscores
Adds support for subqueries
Enables passing params to Db::query()
Simplifies check for adding params

In all other cases we'll want to append the params, so this seems cleaner.
Fixes DbTest for consistency
Adds Sql::PLACEHOLDER constant for legibility
Enables casting to string multiple times

This would allow us to capture the last query for logging and profiling, etc.
Adds Sql::buildAliases(), Sql::cond(), Sql::enclose()
Tweaks aliasing tests for clarity
Enables passing params to constructor and appendQuery
Sorts method order by visibility

This makes the code clearer and more organized.
Allows inserting functions as values
Enables merging subqueries via appendQuery

In this case we don't want the subquery enclosed in brackets automatically.
Merge pull request #31 from zeebinz/feature/sql-extensions

Sql: extend supported syntax