remisphere

You should not be allowed to mix elements from different dimensions, so in case of multiple element decompositions, maybe allow (or impose) to specify the dimension name before the opening...

For the `h[top bottom]` vs `[top bottom]` part, I was trying to anticipate cases where you would also want to rearrange dimensions, like ```python rearrange(imgs, 'c[rgb a] h[top bottom] ->...

This would also be useful when working with Pandas' [MultiIndex](http://pandas.pydata.org/pandas-docs/stable/user_guide/advanced.html#hierarchical-indexing-multiindex), with the option to choose a particular level that encompasses several samples. For example, I am working with a dataset...

It seems like the config file does not resolve paths : to get the database in `~/.cache/duc.db`, neither `~/.cache/duc.db` nor `$HOME/.cache/duc.db` worked, I had to give the full expanded path...

I couldn't get it to work. Now I get errors like this: `Error opening: /home/myName/~ - Database not found`, `Error opening: /home/myName/$HOME - Database not found` I'm running Ubuntu 19.04,...