Test on PHP7

[problem]
Couldn't enter a user record.

[cause]
`group_id` was set to "NOT NULL" but MySQL in the development version allowed the script to insert records without specifing the value of `group_id`. The MySQL in php7 was strict and so it generated the error.

[solution]
Set `group_id` to "DEFAULT NULL"
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Test on PHP5 & IIS

[problem]
Checkout simulater hangs up.

[cause]
IIS doesn't allow the script to post on the path without registered file extenstion.
Since the path was ".../sim/", it didn't have file extention.

[solution]
Changed ".../sim/" to ".../sim/index.php"
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