When working with any platform version and build numbers update is delegated to developer;
To increase build number a developer has to:
1) do manually
2) create/find a post build script which updates them automatically.
Adding a check box to increase automatically build version should be a nice addition, and a rule to increase major/minor/build version for Version field should be too.
Adding the ability to use a build number flag into Version field, eg: 1.0.$B could be useful too: when building it will replace $B with current build number.
Adding the ability to use a minor increase rule into Version field, eg: 1.$m.$B could be useful too: when building it will replace $B with current build number and using a number field which set after how many build to increase minor $m field will be changed properly.
"Increase minor version after x builds" FIELD VALUE: 10 (using 0 means don't increase)
Result version: 1.0.0
Result version: 1.0.5
Result version: 1.1.0
and so on...
Android platform requires to use different build number when sending versions so a developer has to remember to change build number if it keeps the same version to avoid errors when uploading (or he has to delete previous build with the same build number from the play developer area before).