Display values of 1 throttle.up in the first part of status bar

[chros73]

Display values of 1 throttle.up in the first part of status bar.
Currently the beginning of status bar looked like this:
[Throttle 500/1500 KB] [Rate: 441.6/981.3 KB]
Include the max limit of the throttle, the main upload rate and the upload rate of the throttle (in this order):
[Throttle 500 (200)/1500 KB] [Rate: 441.6 (190.0|51.6)/981.3 KB]

• make the displayable throttle.up name configurable via config file: ui.status.throttle_up_name.set
• don't display this extra info in the following cases:

-- there isn't any throttle.up name as the config variable suggest or the given name is "NULL"
-- the throttle.up is not throttled (=0)
-- the global upload is not throttled (=0) (the throttle.up won't be taken into account in this case)