zip() speed tweak: only use cycling iterators when lists are ragged.
New shell import command and load command syntax change
Minor speed tweaks:
- avoid cyclic iterators in mapz unless lists are ragged
- add map inliner
- add size inliner
- add zip inliner
- misc housekeeping
Check for module's existance before adding to import list
Merge pull request #60 from mcguigan/shell_import

New shell $import command and $load command syntax change