Provide Label Property on Item Class

[JeffFerguson]

The Item class should maintain a property of type string called Label, which will return the label from the Label linkbase matching the fact. If no label is available, then the property should evaluate to an empty string.

The sample available in Issue 12 should be used as an implementation starting point for this work.

[ValeriyTitov]

I think string property is not best way to implement.

1. According article on page 33 in Xbrl in plain english.pdf each concept (fact) can have more than one label (depending on language, fact value, or other conditions). I supose, label should be list of strings or even own class.

Note that we give each label resource for the same concept the same value for the label attribute. This enables us to use a one-to-many link from a concept to all its labels. In this case three different types of label for the nr_employees_total concept.

2. Im unsure if im asking right question for finding labels for fact.
   Because "Flat list of facts with label" is not real life example of xbrl-report. Usually for me - its datatable, with Label in its header.
   However, as i understand, xbrl taxononmy can contain presentation level with description of best look.

[JeffFerguson]

Thank you for the feedback! I'll keep this in mind and read up a bit more before I finalize an implementation.