Document y_array_grep()
Fix some doxygen errors.
Document y_array_filter()
Document y_array_merge()
Document y_array_split(), slightly optimise y_array_merge()

Could not resist mixing changes a bit here.
Fix a few doxygen errors.
Document y_array_shuffle()
Update the include protection tag to use the same format as all the others.
Rename basically all of the param array function parameters to match the current C coding style.
Rename the include protection define for y_transaction.c, add doxygen exclusion tags and update the copyright.

Not sure if I added anything this year, but a) it would not surprise me and b) I'm about to start working on this file for real so it won't be inaccurate for long.
Update a few of the copyright notices to reflect the changes made this year.