Allow export of first 1000 issues seen in Issue Navigator

Problem Definition
Currently, after updating to JIRA 7.5.2, users are no longer able to export the maximum limit of issues allowed (1000) when the JQL returns more than 1000 issues. User are hitting into 403 error on browser.

Further investigation found that in 7.5.2 and newer, JIRA has dropped the use of the &tempMax=1000 by default, and thus would throw the 403 forbidden error.

Previous versions such as 7.5.0 allow the export.

Suggested Solution
Allow the export, but notify the user that only a limited number of issues are exported.

Why this is important
This would make it more convenient for the users to export their issue. Current problem of hitting into the 403 browser error makes it not possible for user to perform the export. The workaround which is to append "&tempMax=1000" at the end of export URL would not be intuitive enough.