Numeric variable with closed interval limit and minus infinity

[Manuel Luque]

If the user creates a Bayesian network, adds a random variable, changes its type to "Numeric", saves the network, and open it again, then the domain of the variable has the lower limit "[-infity", which is closed, but it should be open when having minus infinity.

[Miguel Ángel Artaso Landa]

Specific code added to DiscretizeTablePanel class to deal with the infinitive limits. Commit: https://bitbucket.org/cisiad/org.openmarkov.core.gui/commits/96695824a68199290dd3c2be893ce3ed7a567182