[dox] fix some MSL vs. ellpsiod alt comments
[math] geodetic_int: add extra ecef <-> enu/ned position functions

- ecef_of_enu_point_i has coordinates in cm
- ecef_of_enu_pos_i has ned in meter with INT32_POS_FRAC and ecef with cm
[state] fix local ned/enu to ecef conversion

by using new ecef_of_enu_pos_i functions which have enu in meter with INT32_POS_FRAC and ecef with cm
instead of everything in cm