handle cascaded columns when they are removed from the parent table

If a column is removed from the parent table of a `CascadedTable` the
listener calls `filterColumns(...)`. There `Column` objects for all
indices of `m_pnames` were retrieved, which resulted in a
`IndexOutOfBoundsException`. 
Now, `Column` objects are retrieved by name and checked if they exist.

cp. https://github.com/prefuse/Prefuse/issues/6
Merge pull request #9 from kjkrum/master

Tree layout fixes of spanning tree with custom root node
Allow spaces in JAVA_HOME directory
Merge pull request #10 from Zillode/master

Allow spaces in JAVA_HOME directory (Windows build.bat)
Merge pull request #13 from kjkrum/master

Methods to help with memory leaks; wheel zoom enhancements
Merge pull request #6 from prefuse/cascadedtable-filter

CascadedColumnListener removal bug