Provide a custom repository action for initiating the bulk import tool

[pmonks]

Migrated from https://code.google.com/p/alfresco-bulk-filesystem-import/issues/detail?id=80

Provide a custom repository action [1] for initiating the bulk import tool.

Related to this, there should also be a way to directly monitor the status of an in-progress import, although this can't be done via a custom repository action because actions only support commands, not queries (in the "Command Query Separation Principle" sense of those words).

[1] http://wiki.alfresco.com/wiki/Custom_Actions

[pmonks]

Testing is blocked on Alfresco issue SHA-312, so dropping from Version 2.0 (code remains, but is "use at your own risk" due to lack of testing).