Show "Demo-Cloud" and configuration for Weight classes

See merge request arsnova/topic-cloud!12

Disable further questions and show keywords on questions

See merge request arsnova/topic-cloud!16

# Conflicts:
#	src/app/components/shared/header/header.component.html
#	src/app/components/shared/header/header.component.ts
#	src/assets/i18n/home/de.json
#	src/assets/i18n/home/en.json

added import whitespaces

Merge 'tag-cloud' into 'staging'

See merge request arsnova/topic-cloud!14

[Merge Request: !14]

do not show category drop down when no tags available, fix style, change...

Closes #34

See merge request arsnova/topic-cloud!13

Refactored Filter Options

Merge branch 'questions-to-be-selected' of git.thm.de:arsnova/topic-cloud into questions-to-be-selected

fixed keywords

do not show category drop down when no tags available, fix style, change button background when selected

Add function 'demoToggle' in tag-cloud.component for demo switch.
Add 'demoData.ts' for default demo-data.

This commit is partial and does not support full functionality.
The limitation of the tags within the cloud does not work yet.

[Ticket: #32]

[Ticket: #33]

We needed to use the EventService to bring the data from the
tag-cloud component into the header component. The event is
called every time we analyze new data in the tag cloud.

[Ticket: #16]