Add a simple sequence viewer

[BECATRUE]

Feature you want to implement

To show how the experiment actually ran, we need to analyze the vcd file generated while the experiment is running. For this, we need to implement the followings.

• Fetching the vcd file from the proxy server.
• Parse the vcd file using pyvcd.
• Show the sequence using QTableWidget.

How the feature is implemented

There are two problems to parse the vcd file using pyvcd.

• The timescale 1000ps is invalid, so it should be modified to 1ns.
• The identifier e.g., ttl/ttl0 must not include a slash (/), so it will be replaced into an underscope (_).

Additional context

Unless you know pyvcd well, please see documentation.

[BECATRUE]

According to #119, this issue is cancelled.