hpkg format: Generalize user/global settings file attributes

* For all identifiers: Rename global settings file to global writable
file. We want to use the respective attribute also for other writable
files, not only settings files.
* User settings file/global writable file info/attribute: Add
isDirectory property/child attribute. This allows declaring global/
user settings directories associated with the package.

BPackageInfoContentHandler: Handle new attributes

Also add respective *Data constructors to BUser, BUserSettingsFileInfo,
and BGlobalSettingsFileInfo.

hpkg format: Add attributes for declaring settings files

Global and user settings files can be declared. For global ones an
update policy can be specified. If not specified, the settings file is
not included in the package, but created by the program (or user) later.
If an update type is specified, it defines what to do with the settings
file when updating the package to a newer version.

User settings files are never included in the package; they are always
created by the program or the user. If the package contains a template/
default settings file, it can be declared, but for informative purposes
only.

hpkg format: Generalize user/global settings file attributes

* For all identifiers: Rename global settings file to global writable
file. We want to use the respective attribute also for other writable
files, not only settings files.
* User settings file/global writable file info/attribute: Add
isDirectory property/child attribute. This allows declaring global/
user settings directories associated with the package.

BPackageInfoContentHandler: Handle new attributes

Also add respective *Data constructors to BUser, BUserSettingsFileInfo,
and BGlobalSettingsFileInfo.

hpkg format: Add attributes for declaring settings files

Global and user settings files can be declared. For global ones an
update policy can be specified. If not specified, the settings file is
not included in the package, but created by the program (or user) later.
If an update type is specified, it defines what to do with the settings
file when updating the package to a newer version.

User settings files are never included in the package; they are always
created by the program or the user. If the package contains a template/
default settings file, it can be declared, but for informative purposes
only.