Geodepy

GNSS module
* Add function to remove velocity from sinex
* Add function to only remove zeros from matrix

Survey module
* additional formulae group for calulation of refractive index

This release revises functionality in the `geodepy.survey` module that computes corrections applied to electronic distance measurements. This includes changes to the parameter types and units in the function `geodepy.survey.first_vel_params`

This release adds the ability to handle upper triangular matrices to gnss.remove_stns_sinex()

Fix formatting issue

Changes include:

- Fixed remove_stns_sinex() so that the header line now contains the correct number of parameter estimates and the creation time is correct.
- Four new functions were added:
-- set_creation_time(),
-- read_sinex_header_line(),
-- list_sinex_blocks(), and
-- print_sinex_comments()