INDEX support

[oyerli]

An annotation to create INDEX on columns would be very useful. After the database gets larger, column index become very important for performance.

[satyan]

You can try this pull request.. #64
We're yet to merge it to master..

[maarek]

Any change this can get in?

[howettl]

I created a new pull request: #749 which resolved the merge conflicts from #64 .

[JonatanSalas]

@howettl Thank you for your contribution! I will try to review this PR as soon as I can, the most probably it's that I will review it on Saturday.

[bigntallmike]

Looks good; I'm currently adding indexes with the version migration feature instead (CREATE INDEX IF NOT EXISTS ...) in each of the VERSION.sql files.