lib: Remove unused JARs

For now only XSSF and HSSF is needed, so JARs that are not needed are removed
in accordance with [1]. log4j is already used, so it gets removed, too.

[1]: https://poi.apache.org/overview.html#components
src: gui: wizard: importdata: CsvPage: Hide preview in case of error
src: gui: wizard: importdata: ExcelPage: Hide preview in case of error
src: main: importdata: DataSourceConfiguration: Exception in case column names are not unique
src: main: importdata: DataSourceConfiguration: Exception in case index is not unique
src: main: importdata: CSVFileImportAdapter: Assign header name only if non empty
src: main: importdata: ExcelFileImportAdapter: Assign header name only if non empty
src: gui: wizard: importdata: ColumnPage: Enforce unique column names
src: gui: wizard: importdata: Make error messages more meaningful
src: main: importdata: ExcelFileImportAdapter: Set missing cell policy
src: gui: wizard: importdata: Catch IllegalArgument exceptions, too
src: main: importdata: ExcelFileImportAdapter: Check number of columns for each row
Rename fanout to group
Rename fanout to group
Implement hierarchy editor
Clean up hierarchy editor
Merge pull request #5 from johnpatcher/fix/robustness

Make data import more robust
Merge pull request #6 from johnpatcher/cleanup/importdata

lib: Remove unused JARs
Rework layouting algorithm
Go on with implementing the hierarchy wizard