Docker install :: "URL is taken or contains a reserved word"

Here's the setting: https://github.com/mattermost/platform/blob/master/config/config.json#L21

@eric, could we have your help:

1. Adding this setting to the Configuration Settings guide?

2. Writing up documentation on creating teams and noting this option?

   Basically the option keeps teams from being named with certain reserved words that could potentially conflict with directory names that may be used in future, e.g. Don't allow teams to take up the URL namespace "support" in case in future functionality might need to use domain.com/support as a functional path to get to support.

3. Please open a ticket to link "reserved word" in the UI above to a list of reserved words and an explanation of this feature.

   The functionality would be similar to the "Help" feature under input boxes now on master.