packagefs: Initial support for booting into old states

If an old state is specified via mount parameters we load the packages
as specified in its activated-packages file.

The interface for the package daemon, the package daemon itself, and
the package kit are still to be adjusted, so ATM some PM components
might be a bit confused when an old state was booted.

packagefs: Package: Use PackagesDirectory directly

... instead of Volume. Necessary to support using packages from
different directories.

packagefs: Move Volume::PackagesDirectory to top level

Also make it a BReferenceable and fix Volume::fPackagesDirectory leak.

packagefs: Support blacklisting entries in packages

In each installation location, it is now possible to create a settings
file "packages" that allows to blacklist entries contained in packages.
The format is:

Package <package name> {
EntryBlacklist {
<entry path>
...
}
}
...

<package name> is the base name (no version) of the respective package
(e.g. "haiku"), <entry path> is an installation location relative path
(e.g. "add-ons/Translators/FooTranslator").

Blacklisted entries will be ignored by packagefs, i.e. they won't appear
in the file system. This addresses the issue that it may be necessary to
remove a problematic file (e.g. driver, add-on, or library), which would
otherwise require editing the containing package file.

The settings file is not not "live". Changes take effect only after
reboot (respectively when remounting the concerned packagefs volume).

packagefs: Share string instances globally

Introduce a class String which refers to shared private data that is
registered in a global hash table (in class StringPool) and use the
class consequently. This eliminates duplicate allocations for the same
string and also speeds up tests for equality. There's quite a bit
overhead for the management structures (apparently even more than for
the string data itself), but due to almost all strings being used
multiple times this still almost halves the memory usage for string
data.

packagefs: Organize sources into subdirectories

packagefs: Initial support for booting into old states

If an old state is specified via mount parameters we load the packages
as specified in its activated-packages file.

The interface for the package daemon, the package daemon itself, and
the package kit are still to be adjusted, so ATM some PM components
might be a bit confused when an old state was booted.

packagefs: Package: Use PackagesDirectory directly

... instead of Volume. Necessary to support using packages from
different directories.

packagefs: Move Volume::PackagesDirectory to top level

Also make it a BReferenceable and fix Volume::fPackagesDirectory leak.

packagefs: Support blacklisting entries in packages

In each installation location, it is now possible to create a settings
file "packages" that allows to blacklist entries contained in packages.
The format is:

Package <package name> {
EntryBlacklist {
<entry path>
...
}
}
...

<package name> is the base name (no version) of the respective package
(e.g. "haiku"), <entry path> is an installation location relative path
(e.g. "add-ons/Translators/FooTranslator").

Blacklisted entries will be ignored by packagefs, i.e. they won't appear
in the file system. This addresses the issue that it may be necessary to
remove a problematic file (e.g. driver, add-on, or library), which would
otherwise require editing the containing package file.

The settings file is not not "live". Changes take effect only after
reboot (respectively when remounting the concerned packagefs volume).

packagefs: Share string instances globally

Introduce a class String which refers to shared private data that is
registered in a global hash table (in class StringPool) and use the
class consequently. This eliminates duplicate allocations for the same
string and also speeds up tests for equality. There's quite a bit
overhead for the management structures (apparently even more than for
the string data itself), but due to almost all strings being used
multiple times this still almost halves the memory usage for string
data.

packagefs: Organize sources into subdirectories