Session migrations should be encapsulated and cleaned up

[bsclifton]

See comments at
#10181 (comment)

Not that we have to do it now... but I'm Curious what you think @diracdeltas and @darkdh

Similar to Ruby and Python, maybe we could create a /migrations/ folder and have a single file (ex: 0-20-0_1st_3rd_fingerprint) with a two possible functions (postMigrate, preMigrate) for each type of migration that we'd like to run.

We could then call them like so:

module.exports.runPostMigrations = (data) => {
 migrations = [
   require('../migrations/0-12-0_search_xml'),
   require('../migrations/0-14-0_autofill_data'),
   require('../migrations/0-20-0_1st_3rd_fingerprint')
 ]
 migrations.runPostMigrations()
}

cc: @diracdeltas @NejcZdovc @darkdh