Replicate Bio-Formats Importer dialog as an ImageJ2 command

[ctrueden]

When opening an image (either via File > Open or at least File > Import > Image), we want to show a dialog similar to the one shown by the Bio-Formats Importer. Some of the options there are made obsolete by SCIFIO, but many are still relevant. Part of addressing this issue is addressing exactly which are which.

[ctrueden]

Migrating OME ticket #4164 here, too:

Instead of the current color options, we could have a "Specify custom color settings" checkbox. If that box is checked, then a later dialog with all of the custom color options would appear.

In addition to the options already present, the color options dialog should contain an option to constrain all channels to the same display range.