Convertor: Validate the received value for 'Rows Limit"

[jrf]

According to the HTML, the row limit is supported to be between 1 and 5000.
Currently this value was not being validated, so negative values or very high values could be passed via a script or when a browser would disregard the min/max as indicated in the HTML.

As a best practice, input should be validated server side anyway.

This minor change adds the necessary validation and ensures that the value is always between 1 and 5000.

[johnjamesjacoby]

In 6661:

Converter: bind number-of-rows attribute to between 1 and 5000.

This change adds validation to ensure no unexpected number of database rows are queried.

Trunk, for 2.6. Props jrf. See #3148.

[johnjamesjacoby]

In 6662:

Converter: bind number-of-rows attribute to between 1 and 5000.

This change adds validation to ensure no unexpected number of database rows are queried, and also back-ports sanitization to database connection values from trunk.

2.5 branch, for 2.5.14. Props jrf. Fixes #3148.