Add T-Mobile Germany MMS settings

Checked with T-mobile web site:

https://www.t-mobile.de/handy-hilfe/0,23626,26974-_,00.html#/samsung/galaxy-s4/mms-und-sms/usecase/mms-manuelle-einstellung/11

Confirmed by TJC users:

https://together.jolla.com/question/38555/mms-issues-hints-for-debugging-and-helping-us-to-improve/#post-id-38866