Token generation page improvements

The following improvements should be implemented on Knox's token generation page:

1. When an error occurred during token generation, the error box is displayed on the page. However, this error box is not hidden upon the next successful token generation time.
2. The previously mentioned error box is very hard to read due to its color (white)
3. It'd be beneficial if the response text was visible in the error box too (e.g. "Unable to get token - token limit exceeded.")
4. Date/time information on token generation and token management pages should use the same time zone and display format