ability to generate shorter dkim keys

[Shubham Prasad]

several domain seller including namecheap and godaddy right now support only 1024 bit long txt field values, therefore there should be a provision to use lower length of key

[Stephan Krebernik]

I used to change line 70 in /opt/admin/src/Analogic/BoxesBundle/Handler/FileSystem.php

$this->exec("cd $path && ".$this->openssl." genrsa -out private 2048 2>&&

but this doesn't seem to work anymore..

[SH]

https://uk.godaddy.com/help/add-a-txt-record-19232 - GoDaddy have 512byte limit now

Since all big email providers use 2048 I don't want lower key length. This line is located at /opt/admin/src/AppBundle/Handler/DKIM.php:35