SoliDry#144. Remove app logic in terms of not entangle generated sources

Merge branch 'develop'

SoliDry#142. Add badges downloads/stable version

SoliDry#134. Add error getter for db

SoliDry#130. Fix Content-Type headers

SoliDry#129. Add rollback system ability for rollback="2019-02-15 15:…

…16:17"

SoliDry#128. Add more titles, description to api:generate command

SoliDry#122. Change readme - mistakes and generated dirs correction

SoliDry#118. Add validate method to check custom and required types

SoliDry#121. Change badges to api-generator + codecov + fix tests