Webpagedownloader supporting different HTTP requests

See merge request !65

Resolve "export should use API"

Closes #100

See merge request !93

CI test for frontend

See merge request !112

when user logout session auth key is cleared

Closes #206

See merge request !111

uploading of big data overlay gives proper error message

See merge request !110

Resolve "test issues"

Closes #203

See merge request !109

first the full query is sent to server, if it resolves properly then we
have result if not then we check all info separated by comma

when showing markers all aliases are rerieved in single query (not one
by one)

query for aliases and reaction is done in single go (not one by one)

tomcat7 is not supported in new debian stretch relase

Resolve "exception when running annotations"

Closes #201

See merge request !108

Resolve "data overlays with defined color are visualized improperly"

Closes #197

See merge request !107