- Banned exZERO(), exONE(), exMINUSHALF() and all this from the interface.

  There is now _ex1() meaning 1, _ex_1() meaning -1, _ex1_2() meaning 1/2
  and so on defined in utils.h and implemented in utils.cpp.  Feel free
  to extend them as it pleases you but use them inside the library only.
- Added more evaluations of trigonometric functions
- Added series expansions for psi(x) and psi(n,x) at all their poles