small fixes in session settings, added datetime picker in session settings, small ui fix in sessions view

small fixes in session settings, added datetime picker in session settings, small ui fix in sessions view

proper form errors for voter email adding

Closes #20

See merge request !23

# Conflicts:
#	management/forms.py

aggregate of multiple small ui cleanups and polishes

See merge request !22

moved template variable description from view to form in add election (like we did for add session) and added table-responsive for template description

last sub issue of #2

See merge request !21

make voter list in session detail scroll

Closes #16

See merge request !20

add option to disable abstentions for elections

Closes #18

See merge request !19

Feature email when vote starts

See merge request !18

Send E-Mail When Voting Period Starts and use templates for all emails that are sent to users, Issue #10, Milestone !1

export outcome of the election, issue #9

See merge request !17