Doing inference marks the network as modified

[Francisco Javier Díez]

When doing inference on a network, OpenMarkov marks it as modified, even if we have not changed it.

[Jorge Pérez]

OpenMarkov marks the network as modified whenever an “Undoable Edit” happen. Edits “OpenParenthesis” and “CloseParenthesis”, which are used for compound edits, mark the network as modified. I have added a conditional clause that mark the network as modified for all the "undoable edits" different from these two edits.

Despite that it seems to work, it is important to be aware to possible errors derived from this change.