Provides commands for accessing the mailbox stores.
Folder shouldn't be accessed directly. Instead we use {@link FolderCommand}, which
in conjunction with {@link FolderCommandReference} provide a looking facility.
This makes sure that only one {@link Command} at a time can modify the folder's
data.
As explained in org.columba.command, {@link DefaultProcessor} is a preclaiming
schedular. FolderCommandReference keeps a list of folders involved in
the operation the Command executes. DefaultProcessor will only start
the Command if all folders (resources) can be claimed at once.
This class is used to create a filter based on the currently selected message
(if multiple selected, the first one in the selection array is used) - either
using Subject, To or From.
This class is used to create a virtual folder based on the currently
selected message (if multiple selected, the first one in the selection array
is used) - either using Subject, To or From.