Solve Proxy issues

[frauzufall]

Currently people behind a proxy have issues with updates via HTTPS.

I deleted the rest of the text here because the issue is apparently not in imagej-updater.

[frauzufall]

Since the issue seems to be solvable in IJ1 (imagej/ImageJA#17), the only thing left here to do is to catch the SocketException thrown in this case and fall back to HTTP.

[frauzufall]

We discussed somewhere that these changes made to IJ1 to fix the proxy issue should also go to the updater so that a pure IJ2 installation can also deal with proxies.

I am am wondering though how proxy handling in a pure IJ2 environment would work from user perspective.

In IJ1, the HTTP system properties are set via a PlugIn, so we made sure the HTTPS properties are just set to the same value.

In IJ2, if there is no addon like this (or is there?) and one could argue that both HTTP and HTTPS proxy settings have to be set by the user via system properties and don't necessarily have to be the same.

[imagejan]

There is OptionsProxy, an IJ2 command that is not shown in the legacy UI.

I guess we might have to somehow sync these options in the legacy layer, if they aren't already.
Of course, they're synced in OptionsSynchronizer, so it might be just enough to ask the OptionsService for the current value.