Fixed DateTime parsing.

Leaving _formats[0] uninitialized will cause an exception whenever
DateTime values are parsed using ParseExact(...).
new overlay groups should be a multiple of 2
move Dicom.Dump to Tools directory
remove Mixed Platforms build
restructure distribution package
update NLog to 2.1.0
show/hide overlays and apply custom color (@GMZ)
Merge pull request #56 from captainstark/master

Exception being thrown because DateTime formats array index is off by one.
Merge Remote-tracking branch 'upstream/master'