#127. Added UX language requirement to UC1
Formalized UC9.1/1 using "reads" elementary use case.
Defined front page as a type
Descrition of displayed usage data is updated in UC5
UC11 where User logs out is added.
Merge pull request #178 from andrewbol/Issue-108

#178: pull request UC11 where User logs out is added.
Merge pull request #166 from andrewbol/Issue-42

#42: Description of displayed usage data is updated in UC5
Merge pull request #160 from antonxt/156

Formalized UC9.1/1 using "reads" elementary use case
Merge pull request #153 from antonxt/127

#127. Added UX language requirement to UC1