Merge pull request #1 from johnpatcher/cleanup/importdata

Cleanup/importdata
Rework hierarchy editor code to be (1) cleaner, (2) more efficient
Forked datahandle tests and example
Format and comment examples
Fix method names
Rework aggregate functions and provide examples
Bugfix: use new aggregation functions
Implement base functionality in hierarchy builders
Extend example
Start to implement interval-based hierarchy builder
src: main: importdata: Column: Cleanups and refinements
src: main: importdata: CSVConfiguration: Cleanups and refinements
src: main: importdata: DataSourceConfiguration: Cleanups and refinements
src: main: importdata: Refactor CSVConfiguration
src: main: importdata: Rename CSVConfiguration to CSVFileConfiguration
src: main: importdata: Rename FileConfiguration to DataSourceFileConfiguration
src: main: Move source configuration classes into io package

These classes could theoretically also be used to describe data sinks rather
than sources, so they are moved into a more generic package. Probably it would
also make sense to rename them, as "source" is technically not equal to "sink".
src: main: io: Rename header interface
src: main: io: importdata: DataSourceImportAdapter: Cleanups
src: main: io: importdata: CSVImportAdapter: Cleanups