reworked layout of sending activity

Hi! I didn't really like the messy look of SendMainActivity so I gave it a quick try to create a more organized look. Only changes in layout xml-files, no source code changed.

Feel free to ignore or change this if you don't like it this way (your design goals and preferences may differ and I fully acknowledge that).


Here some (resized) screenshots for comparison before and after:
![old-001](https://cloud.githubusercontent.com/assets/285900/3020620/c89f32ea-dfa1-11e3-98d9-818058f9361a.jpg)
![new-001](https://cloud.githubusercontent.com/assets/285900/3020621/c9cbd010-dfa1-11e3-80ce-9c8e897ef163.jpg)
![old-002](https://cloud.githubusercontent.com/assets/285900/3020623/d55fbd10-dfa1-11e3-872e-723d848869c0.jpg)
![new-002](https://cloud.githubusercontent.com/assets/285900/3020625/d6b42d9a-dfa1-11e3-8995-25de6b4a8641.jpg)
![old-003](https://cloud.githubusercontent.com/assets/285900/3020627/d86e43c8-dfa1-11e3-8ec9-b4787e98eee5.jpg)
![new-003](https://cloud.githubusercontent.com/assets/285900/3020630/da323f16-dfa1-11e3-8ec3-ccbf885743dd.jpg)
![old-004a](https://cloud.githubusercontent.com/assets/285900/3020631/dc3e9138-dfa1-11e3-87f6-ef16810dcebd.jpg)
![new-004a](https://cloud.githubusercontent.com/assets/285900/3020632/de12f850-dfa1-11e3-88f1-142a4446b345.jpg)
![old-005a](https://cloud.githubusercontent.com/assets/285900/3020633/dffbb65c-dfa1-11e3-8971-a390fb9ae012.jpg)
![new-005a](https://cloud.githubusercontent.com/assets/285900/3020634/e1adf3fc-dfa1-11e3-97f9-d7a5c56c85c4.jpg)