TargetArtifact class needs methods to check if is installable and where it will be installed

TargetArtifact::filePath is not enough when a project needs to be installed before it's executed.
I suggest to add the following methods:

• bool isInstallable() const; // true if the target is installable otherwise false
• const QString & installPath(const InstallOptions &opts) const; // computes and returns the path where the target will be after installation.