This patch adds support for Tk options that could be passed as a list or
tuple, for example. I didn't investigate if there are any of these in tk
8.4, but tk 8.5 has this (the padding option for Ttk Label, for example).
Note that this should, if possible, be backported to python 2.5 at
least, since it segfaults here when I pass a list as an option value.

It also aligns some docstrings; documents the support for the 'in_'
option for grid, place and pack, actually all options may end with an
"_", but it is good to document 'in_' specifically because the option
'in' can't be passed "naturally". Lastly it removes the duplicate code
in class Place that checks for the 'in_' option.