[pgAdmin4][PATCH] To fix the issue of EXPLAIN option with IE

Hi,

Please find the patch to fix the issue while using ANALYZE option in IE.

*Issue:*
We were using .startsWith() function to check the sql if it is already
starts with explain clause or not, which was added in commit:
c758920890309e50f47a9427039cf735ddf04d37

But IE do not support .startsWith() function.

- Desktop
- Mobile

FeatureChromeFirefox (Gecko)EdgeInternet ExplorerOperaSafari
Basic support 41 17
<https://developer.mozilla.org/en-US/Firefox/Releases/17> (17) (Yes)
No support 28 9

But IE do not support .startsWith() function.

I have also changed the code for File Manager module as well for the same
issue.

So affected modules are,
- Query tool
- File Manager

Please review.
RM#2347

--
Regards,
Murtuza Zabuawala
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company