Some minor reorganisation so that ModelExtension moves use the same code
as the CoreModel moves in order to determine whether the move is
accepted. A by-product of this is that we avoid having two calls to
logLikeFactor(), so there could be an increase in efficiency.
Merge branch 'structalign' of https://github.com/statalign/statalign.git
into structalign

Conflicts:
	src/statalign/base/Mcmc.java
	src/statalign/model/ext/ModelExtManager.java
	src/statalign/model/ext/ModelExtension.java