Make timeout a user setting (bugs #469)

Browser timeout values are much greater than the 10 seconds that was a hard coded value. This change allows the user to specify a longer timeout (up to 2 1/2 minutes) if needed.

For an example here is the receive data timeout values from the Microsoft WinINet API:
WinINet.dll version 4.x 5 minutes
WinINet.dll versions 5.x and 6.x 60 minutes
WinINet.dll versions 7.x and 8.x 30 seconds

Timeouts vary between the different browsers and sometimes revisions as noted above.