Add a warning to RELEASES.md to avoid downgrading ImageJ1

This happened when we uploaded 2.0.0 beta 7: ImageJ 1.x was downgraded
for all Fiji users from 1.47t to 1.47q...

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Bump to pom-scijava 1.49

Signed-off-by: Jenkins <jenkins@dev.loci.wisc.edu>
Bump to pom-scijava 1.50

Signed-off-by: Jenkins <jenkins@dev.loci.wisc.edu>
Bump to pom-scijava 1.51

Signed-off-by: Jenkins <jenkins@dev.loci.wisc.edu>
Fix imports

I am so glad we have release bindings between ImgLib and ImageJ now.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Adjust also ij-io to the new SCIFIO version

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

I am so glad we have release bindings between ImgLib and ImageJ now.

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