Added basic types for catalogue access.
Measures basic functions

Basic functions for creation of units and measures and string functions.
Merge branch 'initial-datamodel' into develop
Added functions for Spherical coordinates.
Changed create unit function to return a unit pointer - malloc is done in the create method.
Added reading of catalogues

Started with parsing catalogue filed.
BUG: problems with copying NSStrings into char arrays.
Added reading of catalogues

Started with parsing catalogue filed.
BUG: problems with copying NSStrings into char arrays.
Changed model from C structs to Objective-C objects.
Added Spherical Coordinates.
Merge branch 'initial-datamodel' into develop