Bump SciJava version

This is required for legacy mode event delegator to work properly.
Otherwise, the ProxySubscribers of the delegator (created while
subscribing) would be GCed before they can do its.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Refactor LegacyInjector#setLegacyService context discovery

This will allow us to use the context to subscribe to specific events in
legacy mode.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Subscribe to SciJava's MacOSX-specific events in legacy mode

...and override the ImageJ 1.x' MacAdapter (which uses a deprecated
method to register a MacOSX-specific event handler that is incompatible
with ImageJ2's method).

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>