formatting of matrices and vectors (1d and 2d)
move the coefficient retrieval for power-series in separate function

* this helps when we change internal representation of power-series
enable alternative display styles for integers
defmacros! allows to simplify define-abstract-formats
add explicit config value for standard integer output
fix alternative integer-display

* exponents need to be formatted
* list of factors may be empty
* mft:integer should really contain only integers
* disable fancy formatting in the exponents of polynomials
adjust the integer-abbrev method, increase default abbrev bound
add formatting for elliptic curves and elementary matrices

also cleanup todo markers