Mms size and imageresize option

Created by: vdveer

Added option to disable image resizing if your plan allows bigger (sized) images. Also added a slider to change the maximum MMS size. My provider only allows 300kb messages and as the messages unencrypted stay below 280k, encrypted version might sometimes go over 300kb. So I added a slider to configure this limit.

ps. My first ever android development so might have overseen something in the preferences. Let me know, but seems to work fine.