Install update

correction of the install script

migration to alembic

fix alembic bug regarding schema handling
It was a mistake. You're right it works but we should add "-i" to sudo command :

<pre>if ! sudo -i -u postgres psql -l | grep -q "^ ${kraken_db_name}"; then echo true; else echo false; fi</pre>

Without "-i" option i get an error/warning : <pre>could not change directory to "/root": Permission denied</pre> but i have a result even.