Add SQL query support in Ruby

[montulli]

new 'sql_query' function that will return a raw SQL query.

• Uses Rails 'sanitize_sql_for_conditions' to prevent SQL injection.
• Adds an 'id_whitelist' to limit searches to just the id fields that are approved. This is similar to hard params

[sergey-koba-mobidev]

Looks promising, @SixiS what do you think?

[SixiS]

Thanks for all the work @montulli - really great idea.
Nice to see people still using this gem!

@sergey-koba-mobidev - I don't really like appending the sql-specific code to all the operator classes.
I have an idea to make the gem more extendible by making it so it can have different sets of evaluators / operators.

It's a bit of work tho, will see if I can get to it in the next few weeks.

[montulli]

Howdy! Any more thoughts or progress on this functionality?

[SixiS]

@montulli - woah, thanks so much for pinging on it after so long!
Working on it now - will have a branch for the new stuff in the next week (for real).