Add support for tables with outbound foreign key constraints.

[erikogan]

This branch allows LHM to migrate tables with (outbound) foreign key constraints by renaming the constraints on the destination table.

[ghost]

Thanks a lot for looking into this! I'm packed with stuff today, will have a look at this tomorrow or Thursday.

[erikogan]

I just realized that the mechanism to generate the constraint names is even less ideal than I thought. It will probably fail if you try to run LHM on a table twice. I’m going to take a stab at improving it this morning, but I have a lot going on.

[erikogan]

The newest commit is a bit more invasive than I’d like, but it solves the problem much more robustly. And sets things up to work on fixing inbound foreign keys as well.

[erikogan]

I just rebased everything off the most recent upstream master and fixed the last of the failing builds. I think this one is good to go.

[ssoroka-se]

tested and works great. +1 for merge. Now we just need self-referential constraints and inbound constraint support.

[pomier]

I tested this, but it didn't work on tables having more than one foreign key.
I had two foreign keys, table_ibfk_1 and table_ibfk_2, and in the new table these two FK got the same name, table_ibfk_3.

[ssoroka-se]

I don't believe I ran in to that problem, even with multiple FKs

[arthurnn]

Thanks for the PR, #77 is a more complete solution, so I will try to get that one merged in.

thanks again.