Global settings improvements and protect against non-acknowledged changes

##### ISSUE TYPE
* Improvement Request

##### COMPONENT NAME
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UI
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##### CLOUDSTACK VERSION
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4.17.*.*
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##### SUMMARY
This request is for improvements for the "Global settings" screen.
1. As any user with correct privileges, Protect against "reset" button press without acknowledgement.
- On the "Global settings" screen there is no guard on the reset button.
- Clicking the reset button should prompt user. "Are you sure you want to reset "value" to "default value".
- Selecting the "Yes or Ok" button would update the value in the database with the default value.
- The "Cancel" button will close the prompt without changing any values.

2. As "Admin", the UI offers a way to update the default value stored in the database.

3. As "Admin", the UI offers an editable regular expression to test against, and enforce formatting for the value and default value.

4. As "Admin", the UI offers the ability to edit the description.

5. Any changes should be logged with before and after values.

6. As "Admin", the UI offers a way to update the "Category" field value.

Start at the Global settings screen and trace the existing reset action and administrator controls. Review how settings are persisted and changes are logged, then define completion as guarded resets plus editable default values, validation, descriptions, categories, and before-and-after audit entries.

Written by the indexing model from the issue text.