Allow enabling developer mode from local package.
[developermode] Implement installing from local package. Contributes to JB#47559
This allows enabling developer mode from local package and thus doesn't require Internet or repository access. The package must not have non-preinstalled requirements. Before installing version in package file name is checked against -preload subpackage.
[developermode] Add repositoryAccessRequired property. Contributes to JB#47056
Repository access may be required if the local package does not exist or it can not be installed for some reason. In that case developer mode settings page must ask for repository access (usually some kind of account).