Audit and fix use of Data, Attributes, and Dimensions.

[dainstber]

Previously we used the term data and dimensions interchangeably. We have since moved to use Attributes when talking about the data within a context and using dimensions to refer too Cloudwatch dimensions. This change was made as part of a larger refactor #19 . In order to unblock the refactor we have merged the PR, despite there being at least one case of the incorrect usage.

We need to audit our use of these terms to ensure consistency.

Metric's Datum are aggregated by dimensions not attributes: [(https://github.com/awslabs/swage/blame/7193ce1285c7502011a12144ef71bdc1dfd3f1c5/metrics-core/src/main/java/software/amazon/swage/metrics/record/cloudwatch/CloudWatchRecorder.java#L353)]