return the scale (if available) from read_block()
adding helper function which checks if a block exists
adding helper function which reads the scale from a block
chenged the move_goldstone_to routine to a shuffle rather than a swap.
thus preserving mass ordering amongst physical states.
first attempt to read the scale from the SLHA output blocks

Not complete yet.
add test for the scale reading
chenged the move_goldstone_to routine to a shuffle rather than a swap.
thus preserving mass ordering amongst physical states.
Merge branch 'development' into fix-goldstone-reorder
refactor move_goldstone_to
resolved conflict.