Store and use ConvDev percentage values returned by the version app
As discussed in https://gitlab.com/gitlab-com/salesforce/issues/169#note_35982164 we decided to calculate ConvDev metrics percentages only in the version app and push the calculated values to Salesforce + return them to the GitLab.
We now need to store & use the percentage values in the GitLab instead of calculating them again.
Change in the version app: https://dev.gitlab.org/gitlab/version-gitlab-com/commit/9127d0016136572d4846199984365efa0b169946