This reverts merge request !733

This reverts merge request !682

Fixes #552

The previous migration actually created values for the key "id", including the
quotes. This one should fill out all missing ids.

Closes #511

Indices in postgresql rely on operators, so they won't be used if you use only functions.

Notice test has been failing due to missing placeholder in index.html
I've tried to use fixtures to substitute that file in test environment but it became too much hassle. Fixtures are not copied to _build directory so I'd need to change file fetching logic. IMO it doesn't worth it since pleroma-fe already has this placeholder merged and all future updated of index.html will include it.