BSA — clarification of SeqRegionOperator.ORDER

The usage of the region_operator==ORDER can be clarified. I did not know this,
but it turns out that ORDER is typically used for describing regions that
don't as such get translated or transcribed as a contiguous stretch of
biopolymers like exons are. Instead, they are often used for the location of
descriptive annotations, such as 'histone binding region' or 'regulatory
elements', or 'homology with mouse p53'.

therefore, I propose to replace the text under ORDER of the enum
SeqRegionOperator box to:

ORDER should be used when the sub-regions are to be taken as an (ordered)
set of sub-regions. Typically, it is used to represent a discontinuous region
to which a descriptive annotation pertains.

accepted