Hash representation for "rowLabels" and "columnLabels"

[jcchuang]

Currently, MatrixState contains two copies of row labels (i.e., terms) and column labels (i.e., topic names).

When MatrixState reads the matrix information associated with a dataset, the received data (saved in MatrixState.data) contains two arrays "terms" and "topics" that are the list of vocabulary used in a topic model and the default names for topics, respectively. Currently, user-defined row labels and column labels are saved as arrays "rowLabels" and "columnLabels" as MatrixState attributes.

In MatrixState.js file:

• Create two new attributes "rowModifiedLabels" and "columnModifiedLabels" of type {number: String} that record only the modified labels.
• Automatically update attributes "rowLabels" and "columnLabels" whenever attributes "rowModifiedLabels" and "columnModifiedLabels" are changed.
• Modify functions rowLabels() and columnLabels() so that they write to (or unset) attributes "rowModifiedLabels" and "columnModifiedLabels".