Additional changes:
- Makefile verbosity control
- nimble.sh can now run in parallel on the same *.nimble file
- nimble.sh no longer used in the Makefile, in favour of a nimbus.nims
symlink that eliminates race risks in parallel jobs
- nimbus.nimble takes extra params in the command line, with the caveat
that they also apply to nim
- setCommand() replaced with exec(), to avoid splitting param strings
- isolate dependencies (both Git repos and ".nimble" dir) in "vendor"
- ensure that everything is compiled using our version of Nim with
something as simple as "make"
- pull the latest changes with "make update"
- re-create Nimble's package dir and re-build the Nim compiler automatically when needed
- "env.sh" script that can be used to prefix any command that needs to use
"nim" or "nimble" from our Nim repo
- move the top level nim.cfg to nimbus/nim.cfg so it doesn't apply to
deps
- "fetch-dlls" `make` target for Windows to get precompiled Snappy, RocksDB and SQLite DLLs