BUG: Replaced re with fnmatch

regular expression fails to match expressions with special characters. Structures created for volume nodes containing parentheses and brackets would not show up in structures table.
fnmatch can match expressions containing these characters.

ENH: Left zero padding for structure numbers

Without left zero padding sorting the structure table based on structure number
is not as it is expected.

ENH: Resize per-structure table columns based on contens not fixed values.

ENH: Add new label for a structure only if it is not in the scene.

In the current behavior if one structure exist, adding the same structure will create duplicate labels.

git-svn-id: http://svn.slicer.org/Slicer4/trunk@24061 3bd1e089-480b-0410-8dfb-8563597acbee