Only prompt once when setting multiple block opacities

This fixes a bug in which the opacity dialog would open for
each block when changing the opacity for multiple blocks. Now,
only a single opacity value dialog will be used and that opacity
will be set on all the selected blocks.

Change-Id: I5d41b103927c00ae3dfcceb438035a406024d9a4
Fix menu names in multi-block right-click menu

This fixes the names in the right-click menu for multiple
block selection to show the proper plural names.

Change-Id: I6544e143237ca8e52fa9f40e38b2ef056acecd5b
Fix bug when with 'Show Only Block' for multiple blocks

This fixes a bug in which only the first selected block would
be shown when the 'Show Only Block' action was clicked in the
right-click menu for multi-block representations.

Change-Id: I94181048749878d81808da500e61ebfbd7595213
Merge topic 'fix-multi-block-issues' into next

11ee564 Fix bug when with 'Show Only Block' for multiple blocks
88aa079 Fix menu names in multi-block right-click menu
d1a62c8 Only prompt once when setting multiple block opacities