Standardize Timezone, Latitude and Longitude signs

[German Molina]

SketchUp, EnergyPlus, Radiance and other tools use different conventions for the sign in Latitude and Longitude. We need to choose one for Emp and make it very clear. Also, we need to check for the consistency when reading EPW, WEA and SKP files.

EPW files use: - for South, - for West, GMT for TimeZone (i.e. timezone = 15std_meridian)
WEA files use: - for South, + for West, -GMT for TimeZone (i.e. timezone = -15std_meridian)
Gendaylit and Gensky use: - for South, + for West, and uses std_meridian as input (in + West)
SKP use: - for South, - for West, GMT for TimeZone

As for now, EMP_CORE's LOCATION object has the following definitions:

float latitude; //!< The latitude in degrees North (use negative for South)
float longitude; //!< The longitude in degrees West (use negative for East)
float timeZone; //!< in GMT units

Which means that it is using WEA file standards. Need to make sure this is consistent in other functions.