Mark functions as methodOf, rather than property
Update tutorials and ngdoc for clarity

Update tutorial for filtering to provide an example of setting
the filter programmatically.

Update the ngDoc for ui.grid:GridOptions to mark functions as
@methodOf rather than @propertyOf, which should correctly split
these into the methods section of the ui-grid.info site.

Update the ngDoc for ui.grid:GridColumns to break the properties
out into separate ngDoc blocks, which should make them more easily
visible in the ui-grid.info site.  Mark these also as @propertyOf
ui.grid:GridOptions.columnDefs, which should result in these
properties also being visible on columnDefs.
ngDoc updates, focusing on columnDefs

A pass through each module looking for settings that are set
in columnDefs, and completing ngDoc updates for each.
Merge pull request #1457 from PaulL1/documentation-updates

Updates to ngDoc and tutorial