Add some extension to modify keyboards

[InsanusMokrassar]

In case we have some keyboard like InlineKeyboardMarkup or ReplyKeyboardMarkup it would be useful to have some extension to modify them like:

val keyboard: InlineKeyboardMarkup = ...;

keyboard.modified {
    remove(0) // removing of zero line
    replace(0) {
        // standard row workflow
    } // replacing of zero line by a new one
    add { // duplicate of row extension
        // standard row workflow
    }
    modifyRow {
        // standard row workflow with exists row
    }
    row {
        // standard row workflow
    }
}