Fixes #1597: Added `enableAutoLogin` to basic and advanced application templates so "remember me" now works properly

Backend should be always totally closed for indexing by search engine robots

we should not provide one in the package but developers should commit
them when starting a new project so that all share the same versions
and only explicit composer update command will change that.
Escpecially important when deploying to production.

This reverts commit a28e7470.

Cleaned up a few comments ... hope its not my OCD again... :-)

Reverted name to ```closeButton``` to be in sync with the bootstrap ```Alert``` widget.

1. Renamed closeButton to closeButtonOptions. 
2. Generate unique id for each alert box.
3. Moved parent init to the top.

Each flash variable can be mapped to a bootstrap alert type through a configuration array passed to this widget.

Cleaned up redundant code (and a typo missed earlier).

Removed redundant declarations and checks in the code.

Ensure previous CSS classes are not appended and reinitialized in the foreach loop.

Used ```Html::addCssClass``` and ```Html::removeCssClass``` more effectively.

Added closeButton parameter, assignment of CSS class corrected, and added php doc comments.

The previous alert widget within the advanced/basic app does not render multiple flash messages. The current implementation allows display of all flash messages assigned through setFlash. Also a validation is done for allowed bootstrap alert types.