Add IBIS-AMI Tx jitter parameters.

[capn-freako]

Describe the desired new or improved feature.
Parse and handle appropriately the IBIS-AMI Tx jitter parameters (Tx_DCD, etc.).

Expected behavior
Any Tx jitter parameterrs included in the IBIS-AMI model should be recognized and acted upon accordingly.

Screenshots
(n/a)

Desktop (please complete the following information):

• OS: Windows 10
• Python 3.7.6
• PyBERT 3.3.2

Additional context
(n/a)

[capn-freako]

This one's going to get involved.
I've created a branch for working on it: 85-add-ibis-ami-tx-jitter-parameters.
I'm pausing on this, to clear other low hanging fruit.