Configuration validation

[steveworley]

The edit/add form should have validation to prevent bad configuration values as misconfiguration can cause memory leaks and prevent pages from loading.

Example:

X Tick Values: 2010-11, 2011-12, 2012-13, 2013-14

The description states only numeric values are supported but it is not clear that 2010-11 is not a numeric value and can lead to some confusion.