Added performance attributes

[triyam]

Issue #505

Added putAttribute(...) getAttribute(...) getAttributes(...) removeAttribute(...) putMetric(...) getMetric(...) record(...) to the definations.ts file

I recommend to make the changes in the definitions.ts file first and let me review them before starting with the actual implementation.

As you have mentioned, let me know after reviewing whether to move ahead or not

I am new to open-source, your guidance will be helpful

[robingenz]

See #505 (comment)