Added nf_elem_add/sub/set/equal, docs and test code and fixed some issues
with monic nf polys.
Added mul, docs and test and fixed a number of bugs.
Fixed case where nf poly is monic over ZZ and elems are over Q.
Switch on precomputed inverse for QQ case in mul.
Switched to using weak canonicalisation and precomputed powers for performance
speedup.
Use fmpz/fmpq_poly_rem_powers_precomp.
Cleaned up code a little. Added functions which don't canonicalise.
Updated todo.txt.
Added magma profile to version control.
Added nored versions of nf_elem_mul.
Update to use slong instead of long.
Added inversion of elements in number fields.
Added division of number field elements.
Update copyright dates.
Added fast code for add/sub of quadratic nf_elem's. Added nf_elem_swap.
Attempt to make faster path for common denominator (currently broken).
Canonicalise correctly.
Fix bugs which test code found.
Don't rely on aliasing to work before testing it.
Ensure randtest canonicalises and add test for add/sub common denominator path.