Issue on page /user_guide/coordinate_systems.html

[Esteban82]

I wonder if ti would be good idea to add a table comparing the properties of the 3 coordinates systems like.

Some of the properties could be names of the axis, its value, origin of the system, typical uses of the system (within Harmonica/Fatiando?).

[Esteban82]

Maybe something like this: in rst format (I think)

+------------+----------------------+---------------------------+------------------------+
| Axis | Cartesianas (planas) | Geodeticas / geographical | Spherical (geocentric) |
+---+--------+----------------------+---------------------------+------------------------+
| 1 | Name | easting | longitude |
+---+--------+----------------------+----------------------------------------------------+
| 1 | Symbol | x | \lambda |
+---+--------+----------------------+----------------------------------------------------+
| 1 | Unit | m | decimal degrees |
+---+--------+----------------------+---------------------------+------------------------+
| 2 | Name | northing | latitude | spherical latitude |
+---+--------+----------------------+---------------------------+------------------------+
| 2 | Symbol | y | \varphi | \phi |
+---+--------+----------------------+---------------------------+------------------------+
| 2 | Unit | m | decimal degrees |
+---+--------+----------------------+---------------------------+------------------------+
| 3 | Name | upward | height | radio |
+---+--------+----------------------+---------------------------+------------------------+
| 3 | Symbol | z | h | r |
+---+--------+----------------------+---------------------------+------------------------+
| 3 | Unit | m |
+---+--------+---------------------------------------------------------------------------+