Metamorph: fix double value parsing for locales that use a comma separator

See
http://lists.openmicroscopy.org.uk/pipermail/ome-users/2014-November/004864.html

Double.parseDouble does not account for locale, and assumes that the
decimal separator is '.'.
Merge pull request #1411 from melissalinkert/metamorph-locale

Metamorph: fix double value parsing for locales that use a comma separator