Split lfs_migrate command to the bunch of South migrations.

I propose to change custom migration command to the set of self-writen South migrations.

Pros:
1. It's impossible to migrate between minor versions (0.7.2->0.7.5). 
2. We can provide forward and backward migrations to revert any update.
3. 

Cons:
1. It's hard to first time migrate. It's necessary to choose migrations that alredy done and launch
manage.py migrate --fake xxx
where xxxx is number of migration.