add command for cf expansion of power series

* not just (sqrt poly)
hook cf's for quadratics into math-interactor
add documentation to math-output low-level functions
output of parentheses
setup the menu structure manually
use formula output for check torsion command

* introduce finite-tuple output
* fix bug with function args output
refactor mi commands code
separate commands from rendering
disable obsolete Mathematica export
move cont frac output formatting to math-formatter
move poly/series commands to separate file, remove obsolete formatting code
move presentation related code into one file
major refactoring; moving towards math-formatter

* move alignment helpers into separate file
* move some more math-output code to math-formatter
* get rid of math-output-prepare
* add skeletons for implementation of math-formatter interface
implement math-formatter interface
plug math-formatter into math-interactor in put-result%
remove obsolete definition of presentations
add support for colourising and scaling
reenable support for presentation (WIP)
adjust the presentation names in the remaining commands
move string representation hack to math-presentations