Correction of Labeling and Tooltips suggestions

[Zelss]

• Plugins
  • [x] When uninstalling a plugin the window shows operation in process with " Cancel Install" which should be "Cancel Uninstall".
  • [x] In the browser plugins window the trashcan icon has the wrong tooltip
• Layouts
  • [x] In the Layouts window, copy and edit icons have the same tool tip: "Make a copy of this layout"
  • [x] Wherever a tick box with "Is default" appears it could be replaced by "Make Default"