Modify status bar mod to be able to display 1 throttle.down as well

[chros73]

Modify status bar mod (#4) to be able to display 1 throttle.down as well, also change name of config directive.

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

Currently the beginning of status bar looks 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); and main download rate and the download rate of the throttle.

Possible cases look like these:

[Throttle 200 / 500 KB] [Rate 107.4 / 298.6 KB]
[Throttle 200(114) / 500 KB] [Rate 107.0(1.0|105.9) / 307.6 KB]
[Throttle 200 / 500(250) KB] [Rate 124.7 / 298.2(298.2|0.0) KB]
[Throttle 200(114) / 500(250) KB] [Rate 115.9(1.7|114.2) / 333.9(333.9|0.0) KB]

• make the displayable throttle names configurable via config file: ui.status.throttle.up.name and ui.status.throttle.down.name
• don't display this extra info in the following cases:
  • there isn't any throttle name as the config variables suggest or the given name is "NULL"
  • the throttle is not throttled (=0)
  • the global upload/download is not throttled (=0) (the throttle won't be taken into account in this case)

Refers to: #4 .