Rename from IPDB to DB - step two
Final step of rename from IPDB to DB

Also fixed bad repo info the dist.ini files while I was in there.
Make sure that Serializer->store_data always returns a value
Use byes::length instead of length for getting current position of the buffer

This really shouldn't matter, since the buffer should never be marked as
UTF-8, but it doesn't hurt to be careful.
Add 16 bytes of NULLs as a separator between the search tree & data section

Empty records are now indicated by a value == number of nodes

Taken together, these changes make it possible for a verifier to reliably
distinguish between the search tree and data section.

Previously, it would have been possible for the search tree to contain an
arbitrarily long string of NULLs (X empty records), so there was no unique
value that could distinguish the search tree from the data sction.
Work in progress on the MaxMind DB verifier
Add a verification mode to the Serializer

This makes it extra slow but is useful for finding bugs as they occur
Make Serializer _cache attr lazy
Add some additional debugging output to the Serializer class
Add a test for broken handling of large pointers in the Serializer
Fix a very small typo in the definition of pointer thresholds for the Serializer

For want of a subscript days were lost.
Make root_node_num attr private
Add debugging to the File writer
Tweak debugging message
Add a small test that the verifier can verify files we build.

This doesn't catch bugs that occur with large files.
Fix variable name typoe
Write numbers as 0b instead of 0x so we can see the bit pattern
Fix packing of 28 bit records

When we packed the left record before the right, we didn't preserve the middle
byte of the node when writing the right record.

I also simplified the code a little bit by just looking at the middle byte
rather than the whole other side of node.
Add a test for round tripping of utf-8 strings
Add a test for round trip of utf-8 data when written to and read from a file