Migration procedure.

When you require to perform this procedure?
- When perl version is changed
- When migration to other OS or distribution occurs

Why do i have to perform this procedure?
- Some modules are vendored with bot
- BDB can vary its on-disk format depending on dbd version that linked with
  perl interpreter itself and its appropriate module.

How can i guess that i miss to perform this procedure?
Most notable symptom is 'BDB0091 DB_VERSION_MISMATCH' in logs and bot admin settings are lost.


Procedure steps.

On source system perform following steps:
1. stop the bot, to unlock and close all files.
2. make a backup
3. prepare target system and copy bot to target system

On target system perform these steps:
1. remove vendor_perl dir in bot' directory
2. run "bash bootstrap.sh" (no quotes) and wait until it successfully build and
   install required modules.
3. run perl bin/cache_import.pl script. It should create cache and exit
   silently.

Now it is possible to run bot without settings loss.