Implementing GUID using boost

I haven't taken a look at the hash table stuff, so I didn't touch that, but I was able to get rid of our (respectable!) guid random number seeding stuff in `guid_init`, etc. I ran the test suite and uncovered one problem which I was able to fix. I also started the program with a moderately sized chart and transactions (my mom's business's books), and everything seems good.
I tested this a bit and if the string has, say, `z` in it, it gets changed to `f`. If the string has too many `-`s in it, the parsing function throws.

I added a `try ... catch` block and return false if I catch anything now.