Cleanup, and big refactoring of the frequency code

One thing has been bothering me for a while: we put the frequency information into a different database from the characters.

As such, at run time, we need to first find the character(s) corresponding to the input code, then for each one of them, create a ChChar, then for each one of them, find the corresponding frequency in the frequency db.

That's just way too many iterations.

What my refactoring does is put the frequency information at build time into the same db as the Chinese characters.

And then, at run time, we get everything from only one database, and **iterate only once** to create the ChChar.

Things should be faster, the code is much simpler.
```
$ git diff --stat wanleung/master
[... snip ...]
 7 files changed, 118 insertions(+), 210 deletions(-)
```

And all that without breaking the public API! \o/