BSA — SeqRegionInvalid not just for wrong StrandTypes

Many methods have an Interval as an input parameter (directly, or indirectly
as part of a SeqAnnotation)

Since Interval can-be-a [Composite]SeqRegion, it would seem logical that all
these methods can raise SeqRegionInvalid as well.

Currently, SeqRegionInvalid can only be raised if the StrandType isn't
appropriate; we think that it's natural to also raise it for wrong
CompositeSeqRegion (e.g., when the CompositeSeqRegion has internal overlaps
in cases wher this does not make sense).

So the issue is 1) allow raising SeqRegionInvalid for reasons other than
wrong strandtype and 2) add this exception to the relevant methods, which
are:

BioSequence

• add_annotation
• seq_interval
  NucleotideSequence
• reverse_complement_interval

Alignment

• get_seq_region

SingleCharacterAlignmentEncode

• get_row_column_interval
• get_row_interval

AnnotationFactory

• create_seq_annotation
  (this one also needs SeqRegionOutOfBounds)

Accepted. The text changes were pervasive, but minor.