auto fill sorting colums in ActiveDataProvider if none are configured
Lazy fallback of label creation for Sort class
Refactor DataColum to use model label for sorting link
DataColumn: Allow setting label of sort link via short syntax

attribute:type:Header should also affect sort link
use `@inheritdoc` for ActiveDataProvider::setSort
added label option to Sort::link()
introduced DataColumn::label property
typos in doc
Refactored DataColumn::renderHeaderCellContent()
Moved label for Sort::link() to html options
Merge pull request #809 from cebe/autoconfig-sorting

Gridview and DataProviders: Autoconfig sorting