minor: make tx fn invocation consistent
support imports and requires for Db function

clojure code can take imports and requires as part of the map that
makes up the database function
minor: change apply for InvokeTxFunction
add missing apply cases for InvokeTxFunction

and reformat code for better code width
rename special case of transaction functions

some code reformatting to reduce code width
transaction functions are a special case of database functions, as they expect a database value as a first parameter, and this argument will be automatically supplied by the transactor.