Data structures for export
Merge remote-tracking branch 'origin/master' into export
Add vars field to exporter table
Added rank field to exporter items and implemented a bunch of convenience methods
Added settings handling to export BaseModel classes and added basic file structure (still subject to change)
Merge branch 'master' into export
Merge remote-tracking branch 'origin/master' into export

Conflicts:
	app/conf/datamodel.conf
	app/version.php
	install/inc/schema_mysql.sql
	support/sql/migrations/73.sql
	support/sql/migrations/74.sql
Restructuring
Merge remote-tracking branch 'origin/master' into export
Basically copied refinery management from import branch.

Once both branches are merged we should go back and unify the refinery
handling in once management class.
Restructuring in export framework
Export improvements
Merge remote-tracking branch 'origin/master' into export
Added feature to create export mapping from XLSX file via CLI tool.

The format is very similar to the one used to create import mappings in
the 'import' branch.
Merge remote-tracking branch 'origin/master' into export
Merge branch 'master' into export
Add empty refinery to make RefineryManager happy
Fix issues found when actually executing the code
First exporter version that minimally works with XML
Added means for export formats to check the export mapping for format-specific errors.

This is useful as the formats may have different interpretations and
restrictions of the export mappings. For instance, an XML document
always has only one root, a restriction that is not necessarily true
for other formats (e.g. CSV, which has no hierarchical structure
whatsoever).