phpdoc: Add usage example to DbStore and IniStore
Add interface Fetchable

This change comes from stashed changes and may be dropped in favor of
`feature/query-interfaces'-branch.
Add Selectable interface

This change comes from stashed changes and may be dropped in favor of
`feature/query-interfaces'-branch.
Puppet: Create all icingaweb2 config directories using one `file' call
Remove `DatasourceInterface' in favor of `Selectable'

This change comes from stashed changes and may be dropped in favor of
`feature/query-interfaces'-branch.
DataArray: Let `DataSource' implement `Selectable'

This change comes from stashed changes and may be included in the
`feature/query-interfaces'-branch.
DataArray/Query: Implement abstract functions inherited from `BaseQuery'

This change comes from stashed changes and may be included in the
`feature/query-interfaces'-branch.