Care for needs of growing numbers of mobile / multi-/moving-location users (uploaders)

[hpvd]

More and more things from webusers are done on the go or all the time while moving from place to place
With this one should care for these scenarios.

1. Give mobile / multi-/moving-location users needed information:

a) how big is the file in total they want to upload / they are uploading
as early as possible in uploading process
(nearly all mobile users have a data limit per month)
-> show filesize

b) sometimes one wants to and has a chance to wait until upload is finished before changing the network
-> show remaining time

2. Give mobile / multi-/moving-location users a possibility to react when they change the used network

a) Starting an 1 GB upload in background in WLAN is fine - but when changing network during upload to 3G this may look completly different
-> pausing + restart function

3. make sure, upload with network and with this IP changing is working nicely
   (e.g. from wlan to 3G to other wlan)

a) -> check implementation
(maybe also with continous automatic build testing?)

b) -> give advise on needs in server configs

see: tus/tus.io#90

The client implementations, however, need to handle these cases correctly.

[arturi]

Adding points that have not been addressed yet to #65

[hedgerh]

Another thing, we may want to warn mobile users if they are about to upload a large file, advising them to make sure that they are on wifi beforehand. Options could be passed to the uploader plugins to enable/disable the warning and specify a threshold file size.

Some developers may even want the option to outright disallow uploads > a certain size from mobile users, kind of like how iOS won't allow large app downloads off wifi. Now that I think of it, we should also have options to set limits on uploaded file sizes in general.