OCSADV-27: Declination limits and Coordinates Difference

On this PR the limits for declination or changed to allow 90 degrees and CoordinatesDiff is rewritten in Scala using the new model classes

I wish I could do more thorough tests but I couldn't find the source of the algorithm nor some well known table of differences to compare
I propose we stick with Spiewak and Copeland's [Scala Style Guide](http://docs.scala-lang.org/style) on the scala-lang site.  In particular see the section on [curly-braces](http://docs.scala-lang.org/style/control-structures.html#curly-braces) and [trivial conditionals](http://docs.scala-lang.org/style/control-structures.html#trivial-conditionals).  So here

````scala
if (sinpa < 0.0) Math.PI * 2 - pphi else pphi
````

I think this is consistent with most non-Gemini Scala code that you see out there.  Any objections?