[lmi] Style guide

[Vadim Zeitlin]

 Hello,

 Seeing the commits changing the names of the member variables made me
realize that I never finished writing the style guide where I wanted to
collect all the coding conventions for lmi. However it does contain a few
useful things already (and probably misses many others, but I have to admit
that I started writing it such a long time ago, that I don't even remember
any more what did I plan to add to it) and I wonder if it could be useful
to commit it to lmi repository even in its current, unfinished state. To
give you an idea of what's there, I've created

        https://github.com/vadz/lmi/wiki/Style-guide

with the contents of this Markdown file.

 What do you think, both of its contents and of the idea of committing it?
VZ