fimd symbols cmd

bit of a hack to get a list: is it really impossible to get the varargout
of one function as a cell array?  feel like I solved this before...
python_sympy_cmd: use outputs from python rather than nargout

I left a warning if they don't match (i don't think this is standard practice, but might help catch some bugs for now)
better return values from ipc

use code generation in python to write octave code, then call eval()
with new ipc return we can start to drop _raw, here fix size
findsymbols: use new ipc return, fix for matrix input
add a debug command for python code
no more _raw usage, some string escaping fixes too

also a fix needed to run on matlab where " cannot be used for strings (replace the ' in sympy srepr with '')
bug fix: multidim cell arrays would only have some elements passed to python

basically, unless you *know* you have a vector don't use "length()", use numel instead
clean up sympy_cmd comments and remove the "retcell" version

"retcell" was just temporary for findsymbols anyway, but now everything runs python_sympy_cmd
bug fix: multidim cell arrays would only have some elements passed to python

basically, unless you *know* you have a vector don't use "length()", use numel instead
Merge branch 'ret'

This uses a better technique for return values from python.  Instead of parsing output, we just general octave code in strings and call them with eval()

Still some cleanups from the old approach but its all (mostly?) in private/
run unit tests should do wall time not cputime as we're IO bound (depending on IPC mech)