Fix find_user() method to deal with ambiguous groups

Add error_ambiguous_user() method
Improve user arguments allowing to specify input type (id or name)

Refactor list_users() methods to call find_user(), find_user_by_id() and/or
find_user_by_name() depending on the input.
Fix double whitespace
Merge pull request #1034 from sbesson/rebased/develop/homebrew_uninstall_hudson

Fix Homebrew uninstallation (rebased onto develop)
Update TestNG in blitz to 6.8
Merge pull request #1079 from jburel/fs-image

Add simple method to check if image was imported prior to FS
Small code tidy in handle_tree_selection()
Tree images and selected objects have fileset id
Moving icon selection logic to containers_icon.html

This code will be removed from center_plugin.thumbs.js.html in a subsequent commit
Filesets of selected thumbnails shown in center panel
Fix missing negation in ExportActivity.

This wouldn't cause any problems as the higher-layer logic
already appends the .ome.tiff extension to the file name.
Fix 'wells' de-selection bug from previous commits
Update submodules
merge develop -D org -I include -E exclude: PR 972 (Repository API)
merge develop -D org -I include -E exclude: PR 1047 (Upload)
merge develop -D org -I include -E exclude: PR 1049 (Specification removal)
merge develop -D org -I include -E exclude: PR 1051 (CLI: Improve group arguments allowing to specify input type (see #10677) (rebased onto develop))
merge develop -D org -I include -E exclude: PR 1058 (Fs file caching (#10535))
merge develop -D org -I include -E exclude: PR 1062 (Import log)
merge develop -D org -I include -E exclude: PR 1075 (Connection (rebased onto develop))