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)
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
Merge pull request #1086 from jburel/rebased/develop/big-image-compression

set the compression to high for big images (see #10759) (rebased onto develop)
travis: Install python-genshi
Blitz image.getFileset() method
Templates use img.fileset.id.val don't load filesets
Show fileset thumbnails in right panel for Images
webgateway birds_eye_view uses thumbnail. See #10626
Big Image zooms out to fit window by default. See #8475
Removed rendering query from birds_eye_view src. See #10626

Since we are just using the thumbnail here, we don't want to make a new request to server when
the rendering settings change. Browser can reuse the thumbnail it already has
Only _load() viewport ONCE on Rendering Save/reset

This bug was causing setupTiles() to be called mulitiple times, which resulted in
many unecessary tiles being requested by the big image viewer