Resolve "participant home screen - html template"

Closes #20 and #22

See merge request swtp-block-ws17/arsnova-angular-frontend!63

Reformat join room component
Reformat participant home screen component
Add some basic scss formats

Resolve "comment creation - participant component logic"

Closes #51 and #45

See merge request swtp-block-ws17/arsnova-angular-frontend!46

Resolve "creator home screen - html template (list)"

Closes #47

See merge request swtp-block-ws17/arsnova-angular-frontend!60

Adjust demo data

Resolve "login screen - login component logic" - fix

Closes #57

See merge request swtp-block-ws17/arsnova-angular-frontend!56

Create guestLogin method

Add check for valid email address as username

Resolve "login screen - password reset component logic"

Closes #49

See merge request swtp-block-ws17/arsnova-angular-frontend!53

Use angular-flex for form
Implement FormControl and Matcher