This commit changes the local Tx variables from "t" to "tx". This is partly
for consistency with external documentation but also because it just
annoys me for some reason.
I consolidated the DB.Tx() and DB.RWTx() calls into a single
DB.Begin(writable bool) call. This is more consistent with the
database/sql library.
I also changed the DB.Do() and DB.With() call to DB.Update() and
DB.View(), respectively. This is more intuitive and more inline with
other database verbiage.
Functions such as DB.Put(), DB.Get(), and DB.Delete() were originally
added to be easy to use, however, after implementing Bolt in multiple
projects I have found these ease-of-use functions useless. Nearly
every use case requires multiple calls in a single transaction.
Using the DB ease of use functions turned out to be an antipattern.
I changed the Transaction/RWTransaction types to Tx/RWTx, respectively. This makes the naming
more consistent with other packages such as database/sql. The txnid is changed to txid as well.
