Added sample code for redefining "rake notes" task.
Redefined "rake notes" task so that users may get "TODO" annotations under any
of the spellings "TODO", "TO-DO", or "to-do".
Removed "pseudo-code" comments now that the code has been implemented and they have been rendered redundant.
Factored code out of check_header_list into new method get_trait_and_covariate_info.
Updated validate_csv_data to handle trait data sets.
In validate_csv_data, use the trait_data? test to prevent unnecessary work when dealing with yield data.
Added new trait-related keys to ERROR_MESSAGE_MAP.
Factored code out of BulkUploadController's insert_data action into new
insert_data method of BulkUploadDataSet.
Set @is_yield_data in the initialization method so trait_data? and yield_data?
query methods return correct results right off the bat.  Don't use a separate
@is_trait_data instance variable to mark the data set but simply rely on
negating @is_yield_data.

In get_insertion_data, factor out code for getting variable value attributes
from a data row into trait and yield-specific methods.

Implemented insert_data and its helper methods so that it now works with trait data.

Eliminated trailing whitespace on several lines.