patch for messagesSv.php

Here is an update for the Swedish message file. The patch does the following:

*adds missing messages
*improves some translations in the context they are used
*fixes some typos
*makes some small grammar improvements
*makes some messages consistent in use of language
*capitalises nstab-messages consistently
*removes plural from 'historysize', since units are usually not pluralised in Swedish
*removes some plurals that makes no difference

Version: 1.12.x
Severity: enhancement

Attached: