Added angle utility functions for conversion between degrees and radians and for normalisation.
Added to gitignore

Added user files to gitignore
DEBUG: Normalisation of angles

Normalisation of angles did not return the correct value for negative angles. Added some tests.
Added conversion methods for Julian Day

Added methods to convert between Julian day and time interval since 1970.
NSDate category with Julian Day

Created NSDate category providing methods to create an NSDate from a Julian Day and get the Julian Day from an NSDate object.
Added AKAngularDifference

This function calculates the difference between two angles.
Time system conversions

TAI-TT conversions
started on UTC-TAI conversion (with constant number of leap seconds).
Added time functions for TAI and UTC

Implemented leap seconds (needed for conversion between TAI and UTC). Leap seconds are downloaded if necessary from http://www.ietf.org/timezones/data/leap-seconds.list.
Added Geocentric Coordinate Time and NSDate additions

Added support for Geocentric Coordinate Time.
Added access method (inits, class methods, and getters) for the NSTimeInterval for the supported time systems.
Added access methods (inits, class methods, and getters) for the Julian Day in the different supported time systems.
Merge branch 'refs/heads/time-functions' into develop
Started on Coordinate functions

Created struct for points in spherical coordinates (3D).
Julian Year and Besselian Year added

Julian and Besselian Year methods added to the time functions. Included are NSDate additions for accessing standard epochs.

BUGFIX: The leap second file was opened en parsed every time leap seconds were needed. This is fixed.
BUGFIX: Leap seconds were downloaded from the internet every time the leap second file was accessed because the date of last check was not updated correctly.
Merge branch 'refs/heads/time-functions' into develop
Merge branch 'refs/heads/develop' into coordinate-functions
Added celestial point struct

Added celestial point struct denoting a position on the celestial sphere.
This includes an equinox and epoch (time dimension).
Added Julian Centuries

Added the number of Julian Centuries since J2000.0.
TODO: This value is now calculated in UTC, should probably be UT1.
Added Geographical location types.

Added AKAngle for angles in radians. Changed some utility functions to reflect these changes.
Added AKMakeGeographicalPoint
Coordinate systems added

Enumerations
Added Sidereal Time functions

Started on Sidereal Time.