Add indexes to SQL fields (and other changes)

[qligier]

See #531 and #513 for comments.

[electerious]

Thanks! Will try to publish v3.1.1 this weekend and merge the PR after the release.

Just one thing: The default table structure (https://github.com/electerious/Lychee/blob/master/php/database/photos_table.sql and https://github.com/electerious/Lychee/blob/master/php/database/albums_table.sql) should be adjusted, too.

[electerious]

It says "Could not add index to the album id field!" and outputs "Duplicate key name 'Index_album'" in the log. Update scripts should work no matter how often they get executed. I guess that's the problem.

[qligier]

Right, let's add a test for the indexes:

// Add index to the album id field
$check = Database::execute($connection, Database::prepare($connection, "SHOW INDEX FROM ? WHERE KEY_NAME = 'Index_album'", [LYCHEE_TABLE_PHOTOS]), 'update_030102', __LINE__);
if ($check->num_rows == 0) {
    $query  = Database::prepare($connection, "ALTER TABLE `?` ADD INDEX `Index_album` (`album`)", [LYCHEE_TABLE_PHOTOS]);
    $result = Database::execute($connection, $query, 'update_030102', __LINE__);
    if ($result===false) Response::error('Could not add index to the album id field!');
}

// Add index to the star field
$check = Database::execute($connection, Database::prepare($connection, "SHOW INDEX FROM ? WHERE KEY_NAME = 'Index_star'", [LYCHEE_TABLE_PHOTOS]), 'update_030102', __LINE__);
if ($check->num_rows == 0) {
    $query  = Database::prepare($connection, "ALTER TABLE `?` ADD INDEX `Index_star` (`star`)", [LYCHEE_TABLE_PHOTOS]);
    $result = Database::execute($connection, $query, 'update_030102', __LINE__);
    if ($result===false) Response::error('Could not add index to the star field!');
}

I don't have time to test it yet nor to create the PR, sorry.
Edit: add index only if the test doesn't return rows

[electerious]

Fixed. Thanks!