Ref. for first occurrence of constraint matrix in crystallography

Thanks to David Watkin
Earlier reference for restraint weighting

Thanks to David Watkin
Remove useless citation for SHELXL.

As the reference has already be given earlier, it is not necessary to
repeat it at that position.
CRYSTALS uses the same detwinning for Fourier maps as SHEXL and JANA

Thanks to David Watkin.
Clarify the instructions for authors about PLAT732
Change the notation for the set of symmetry ops.

\cal{O} collided with the notation of eqn (51) one page earlier.
Give earlier reference to Rollet

Thanks to David Watkin

Also a verb was missing and remove another redundant citation of
SHELXL.
Spell out the "adapted formula" for the norm of u
The first formula is coordinate frame-independent