Implements a configurable wait class

For things a test needs to wait for that aren't Watir elements
Watir::Wait hard-codes the polling interval to 0.1 (which makes sense when checking for element-related things)
With this Watirmark::Wait implementation, the poll interval can be set for a longer peried for things like API or Database updates or anything that is expected to take longer to show up that shouldn't be pinged as frequently.
This has the additional advantage of making any direct references to 'sleep'  in other places in test code to be a recognizable bad practice.