More custom words.

git-svn-id: http://svn.code.sf.net/p/picard/code/trunk@1516 8bce386e-0d6e-43e0-b1ca-608082c0432d
Fixed isSimpleInsertion() and isSimpleDeletion() in the VariantContext, per Tim's long-ago request.
They now both check that the first base of ref is equal to the first base of alt.
Added isSimpleIndel() too.
Added unit test to cover the case of complex substitutions (the motivation for this report).



git-svn-id: http://svn.code.sf.net/p/picard/code/trunk@1517 8bce386e-0d6e-43e0-b1ca-608082c0432d
Merge remote-tracking branch 'upstream'