* Transform GitHub saver to work with GitLab as well
You can choose which provider you want to use, the data is given in the
same place.
I tried to avoid code duplication, so service providers' unique
properties are in separate files, the settings of the selected provider
are loaded.
In two fields I am not sure that it fits into the current structure:
* module-type: gitservice
Which module is a `gitservice` type, it will be listed in the
drop-down menu.
* default-api-url: https://gitlab.com/api/v4
The default URL to access the provider's API.
This is just a sketch, not a final version, suggestions for modification
are welcome!
* Rename saver from GitHub to GitService, update docs
* Split GitHub and GitLab to separate savers, apply common lingo
Sadly, it doesn't seem to make much sense to search for common parts in
the code, because there might be a Git service that is very different
from the GitHub API (such as BitBucket). Therefore, I feel that Git
savers are not able to share other than the translations.
I deleted the defaults values from the translations and set it to the
text entry because they should not depend on the translations.
* Add more information about the password field
It is not clear how to create a personal access token, thus added a link
to the help pages. In addition, GitLab only accepts personal access
token, GitHub also accepts the password, so I made this clear.
* Extract commit message to lingo
* Fix indentation
* Use improved base64 encoder
Fix conflict with a06acc4eb8
