Adding context variables through the context-table
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One can add variables to the context, of type int/float/array, through the
context-table; by selecting one of the variables in the table and either
clicking the 'Page Down' or 'Insert' keys. (These are the keys used in the
TabularEditor for 'append' and 'insert' operations, respectively.) Since the
index is not very important in the context-table, the new variable is added
directly to the context, and appended to the current list of block-variables.

A UI pops up to add 'Name' and 'Value'. 'Name' should be a valid string; and
'Value' can be of the following formats:
1. float
2. int
3. Using numpy functions:
    a. numpy.ndarray(...) or numpy.arange(...) or numpy.array(...)
    b. ndarray(...) or arange(...) or array(...); without package name.
