starting to play with printing a calendar
huge commit (too many things to explain in a title)

 * all structures have been transformed:
    - separate structure for planetary data
    - separate structure for astrological data
    - separate structure for year
 * adding some (very simple) astrology
 * new function to get the new year, but will be extended to get any
   tibetan date
 * other minor changes and optimizations
moving structure definitions to tbstructures.(c|h)
oops, forgotten in last commit
Removing the now useless tbcal.(c|h)
small fixes in the ui
Adding Earth Lord computation

* from tcg t4.c, refactored (220 lines -> 71 lines)
* also always using astro_data instead of astro
Adding a function to check for feasts
Functions to print the Earth-Lords and Anniversaries

* also renaming month->month_type to month->type
Adding month astrology (chinese month, animal, gender and element)
A litte check for delayed month for anniversaries
Fixing error in previous commit
Adding lunar day astrological data
Isolating the jd_to_dow function
Adding a function to get string from the Four elements
Adding more data in day_astro_data

* instead of carrying only the most significant term for yoga and moon
  longitude at daybreak, we now carry the entire list
Finishing a first draft for the function printing a calendar
Adding precisions to the tib_day structure
Adding a function to get tib_day from a tibetan date

transformation of the previous get_new_year function
Commenting adj_zla function and the zeromthfg