Rename the field `election.summary` into `election.shortdesc`

shortdesc is the field used in the elections 0.x, let's keep using it to
reduce database change when updating to 2.x
Remove the frontpage field in the elections table
Rename the number_elected back to seats_elected in the elections table

The field number_elected was named seats_elected on elections 0.x so
let's rename it back to it to avoid changes when updating.
Change the embargoed field from Boolean to Integer

The embargoed field is an Integer field in the elections 0.x database
so revert elections 2.x to the same field format
Remove the `role_required` field in the electionadmingroups table

This field does not exist in elections 0.x and we do not have the
information to enforce the check anyway
Change the __tablename__ from electionadmingroups to electionadmins

electionadmins is the name of the table in elections 0.x, so let's be
consistent with it instead of requiring a rename of the table on the
database
Fix the order_by date to order in the dates in descending order
Fix the default title in the base master
Give the total number of candidates in the view_election table
Cover case where there has been 0 votes, thus fixing the division by 0
When importing multiple candidates flash the number of candidates imported

It is simpler to check if all the candidates were imported correctly and
easier to read.
pep8 fixes
Fix import the configuration file specified by the environment variable
Fix ordering of the imports
Add sql upgrade script, allowing to convert the database from elections v1 to v2
Add a dedicated is_authenticated method and use it in the decorators
Set flask.g.fas_user to None upon logout
If the user is authenticated, only show election that the user can vote on

If the user is authenticated, retrieve the list of elections the user has
already voted on, this list is then used to only show the link `Vote now!`
on elections the user has not already voted on
Order the results returned by elections.search() by election date (most recent first)
List all the elections to the admins