Adds the ability to use `$OS`  and `$ARCH`  variables in clients.config and plugins.config(updateURL.* only)

WIP - not hooked in, untested - target 1.8.0 / 0.9.54
Requires significant changes to TrackerClient
Adapted from mtn branch i2p.i2p.zzz.udpsnark (2014)
Ref: Proposal 160

Turn jump button-links back into regular-looking hyperlinks when resolution indicates we are not on a mobile device

otherwise relative to plugin name, as before

Linkify start/stop webapp on password page

Required for irc.ilita.i2p

so that torrents stop when the router stops and restart when the router restarts.

- Use BWLimits from the DirMonitor as a periodic test that the router is there
- DirMonitor does not attempt to autostart torrents if BWLimits test fails
- DirMonitor does autostart existing torrents when BWLimits test passes again
- Register disconnect listener with socket manger and stop all torrents on disconnect
- Use stopTorrent(true) on router errors to prevent changing the persisted torrent running status
- Change autostart default to true for standalone

Possibly more todo for corner cases or other start/stop/fail scenarios.

as requested by R4SAS