Handle connection failures in uploads

### Actual behaviour
- Tell us what happens
the file upload stops and no progress is done - It feels like no error handling is happening because of a very long timeout. File Size: 7MB, breaks after 4 to 11 percent.
### Expected behaviour
- Tell us what should happen
* the app may reconnect and upload the rest of the file if possible
* try uploads in smaller chunks (for example 0.5 MB)
* fail in a minute if not a single byte is transferred
* If missing: handle connection errors

### Steps to reproduce
1. select a list of files
2. click upload

### Environment data
Android version:
5
Device model:
Nexus 10
Stock or customized system:
Stock
Nextcloud app version:
3.1
Nextcloud server version:
13