History: Make sei more permissive

Source of version: 2 (current)

||Valid:|sei do broda Invalid|sei do broda do se'u|| sei requires that the last bit be a selbri, making it sort of Subject-Object-Verb. This is odd. The following choice, added to the start of the free rule in the PEG grammar, seems to fix this: ^SEI-clause free* sentence SEhU-clause^ No significant testing has been done as of yet.