Allow user to disable automatic category cache rebuilding

Right now configuration setting "Quick Section Permission Rebuild" is enabled by default, which prevents progress bar popup to appear when changes to category structure (add/edit/delete) are made. This also imposes, that category permission cache is done in one step in background.

When category count increases (and I doubt that most of developers/users knows about "Quick Section Permission Rebuild" setting) it leads to memory leak and inability to perform automatic category permission cache rebuilding.

To solve this "Quick Section Permission Rebuild" setting can be disabled and then category cache rebuilding would happen using progress bar.

I'm proposing to add more flexibility in terms of configuring how category permission cache will be rebuild and when by creating new configuration setting "Category Cache Rebuild Mode", that will replace "quick category cache rebuild" option with following options:

• Manual - user need to click on rebuild button in catalog (will use progress bar)
• Silent - cache will be rebuild in background (no progress bar)
• Automatic - ask/don't ask user (based on category count) and rebuild (if he agrees) with progress bar

Default setting will be set to Automatic for backwards compatibility.