Corrected several long-standing issues with SIFT-linear and

Corrected several long-standing issues with SIFT-linear and
blockmatching-elastic layer alignment as listed below.  Reduced code
duplication and fixed warnings for parameter shadowing, rawtypes and
unchecked casts.

# forward and backward propagation of transformations beyond the aligned
  layer range (re-)enabled for both SIFT-linear and blockmatching-elastic
  alignment
# blockmatching-elastic alignment now respects the seelected reference and
  does not deform it
# both SIFT-linear and blockmatching-elastic alignment became API methods
  that enable to keep a set of layers fixed
# made SIFT extraction service interruptable
# included multiple-hypotheses merging in SIFT-linear alignment improving
  both accuracy and robustness of geometrically consistent feature
  matching