Allow default timeouts for functional tests to be configured in intern.json

[bryanforbes]

Currently, users are required to call Command#setFindTimeout(), Command#setExecuteAsyncTimeout(), and Command#setPageLoadTimeout() somewhere in their functional tests in order to increase the defaults (the default find timeout is 0). It would be very nice to be able to configure these from within intern.json:

{
    "functionalTimeouts": {
        "find": 5000,
        "executeAsync": 10000,
        "pageLoad": 2000
    }
}