* set up leveldb-datastore
* Adds test for leveldb
* pulls in nim-leveldb by url and hash
* Fixes basic tests for leveldbds
* Implements query iterator
* Fixes include path for defaultImpl
* Review comments by Tomasz
* adding batch entry
* add batched put and delete
* add batched tests
* adding batching capabilities to remaining stores
* open db in readonly mode
* make naming consistent
* release prepared statements
* don't use deprecated add
* check file exists on test exit
* remove unused var
* add better path sanytizing
* rebase master
* Bugfixed and moved all checks into path()
* added check for empty basename in order to avoid bug in isValidFilename
* refactored - all filename checks are moved into path() function that constructs this filename
Co-authored-by: Bulat-Ziganshin <bulat.ziganshin@gmail.com>
* add basic query capabilities to fsds
* rename common tests
* make query tests common
* sanitize key
* check it's possible to query keys at same level
