* Break backwards compatibility
* Allow to deserialize only base-data of packages and build
actions to potentially speed up showing tables
* Speed up package search in many cases by only deserializing
base-data (unless details are actually wanted)
* Avoid keeping list of all packages in memory by pushing each package
directly to the JSON array
* Avoid check for database before pushing each package; do it only before
reaching the next database
* Remove no longer required functions
* Only lock the config for writing the reloading the config file
* Make sure all write operations to the database acquire an "update mutex"
to ensure only one write operation happens at a time
* Do *not* acquire any additional locks when reading from a database as it
should be safe to do so even when a write operation happens because
* LMDB read and write transactions can happen at the same time
* The package cache has its own mutex anyways
* Write ops to the package cache try to lock the "update mutex" to
prevent writing "old" data to the cache during updates
* Make "lastUpdate" atomic to avoid locking the config when accessing it
* Do HTTP head request first when loading database from mirror to avoid
downloading the full database all the time
* Use the last modification date of the local database file because with
the persistent storage even local database reloads became a bit expensive
Martchus