gui: Improve revert/override/delete warning modals (#7847)

1. Change each modal title text to match the action that is being
   executed (i.e. "Revert" to "Revert Local Additions", "Override" to
   "Override Changes", "Delete" to "Delete Unexpected Items").
2. Change the icons to match the icons used by each action (i.e. arrow-
   circle-down for Revert, arrow-circle-up for Override). Replace the
   broken lock icon for Delete with minus-circle.
3. Rearrange the order in the modal HTML code to simplify it a little.

gui/default/assets/lang/lang-en.json

@@ -26,10 +26,12 @@
    "Anonymous Usage Reporting": "Anonymous Usage Reporting",
    "Anonymous usage report format has changed. Would you like to move to the new format?": "Anonymous usage report format has changed. Would you like to move to the new format?",
    "Are you sure you want to continue?": "Are you sure you want to continue?",
+   "Are you sure you want to override all remote changes?": "Are you sure you want to override all remote changes?",
    "Are you sure you want to permanently delete all these files?": "Are you sure you want to permanently delete all these files?",
    "Are you sure you want to remove device {%name%}?": "Are you sure you want to remove device {{name}}?",
    "Are you sure you want to remove folder {%label%}?": "Are you sure you want to remove folder {{label}}?",
    "Are you sure you want to restore {%count%} files?": "Are you sure you want to restore {{count}} files?",
+   "Are you sure you want to revert all local changes?": "Are you sure you want to revert all local changes?",
    "Are you sure you want to upgrade?": "Are you sure you want to upgrade?",
    "Auto Accept": "Auto Accept",
    "Automatic Crash Reporting": "Automatic Crash Reporting",
@@ -40,6 +42,7 @@
    "Available debug logging facilities:": "Available debug logging facilities:",
    "Be careful!": "Be careful!",
    "Bugs": "Bugs",
+   "Cancel": "Cancel",
    "Changelog": "Changelog",
    "Clean out after": "Clean out after",
    "Cleaning Versions": "Cleaning Versions",
@@ -68,6 +71,7 @@
    "Default Folder": "Default Folder",
    "Default Folder Path": "Default Folder Path",
    "Defaults": "Defaults",
+   "Delete": "Delete",
    "Delete Unexpected Items": "Delete Unexpected Items",
    "Deleted": "Deleted",
    "Deselect All": "Deselect All",