* Replace registerCustomScalarFunction with createCustomFunction
The nice thing about `registerCustomScalarFunction` and
`registerCustomScalarFunction` was that it kept the sqlite calls
of type sqlite3_value_xxx inside kvstore_sqlite.
The big downside however is that the "custom" call is awfully
specific due to the specific function signature it demands.
It is likely that for each different use case, a new version
needs to be added.
In this PR the code gets altered to `createCustomFunction` which
allows to just create a custom function with directly xFunc
signature of sqlite. The downside of this is that you still need
to import sqlite_abi in your local code to have access to each of
the sqlite3_value_xxx and sqlite3_result_xxx calls. These could of
course also be wrapped.
* Fix custom sql func test
* Add build_dcli target and add it to CI
* Fix local imports for dcli
* And use local imports for all other files too
* Use local imports in tests and rlpx protocols
* port kvstore from nim-beacon-chain
* remove old database backends
* use kvstore in trie database
* add sqlite dep
* avoid template param double evaluation
* clean up heterogenous lookup todo
Kim De Mey
Jacek Sieka