PackageInstaller: Run install scripts in the correct directory

* From debugging with the Gobe and Moho installer, scripts define which
folder to run them from. The PackageInstaller is supposed to run the script
in that working directory. The parser seems to have the correct folder in
"installPath" when adding the script as PackageItem, but that code is rather
horrible. I've changed it so PackageScript items also set the path, use
InitPath() to obtain the final working directory and set it before running
the script.
* Both Moho and Gobe create the Deskbar link from that script, the folder
is rewritten in the script via ReplaceAll().
* Correctly running the script makes a bug visible: Dynamically added files
in the install location by these scripts are not removed when uninstalling
the package. When re-installing a package, it is first uninstalled and this
currently gives an error for both Moho and Gobe, since they create some
links in these scripts which never worked before. To install again, the
install folder needs to be deleted manually.
* Some cleanup along the way... sorry.

forgot these files as part of the previous commit


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@36021 a95241bf-73f2-0310-859d-f6bbb57e9c96

PackageInstaller: Run install scripts in the correct directory

* From debugging with the Gobe and Moho installer, scripts define which
folder to run them from. The PackageInstaller is supposed to run the script
in that working directory. The parser seems to have the correct folder in
"installPath" when adding the script as PackageItem, but that code is rather
horrible. I've changed it so PackageScript items also set the path, use
InitPath() to obtain the final working directory and set it before running
the script.
* Both Moho and Gobe create the Deskbar link from that script, the folder
is rewritten in the script via ReplaceAll().
* Correctly running the script makes a bug visible: Dynamically added files
in the install location by these scripts are not removed when uninstalling
the package. When re-installing a package, it is first uninstalled and this
currently gives an error for both Moho and Gobe, since they create some
links in these scripts which never worked before. To install again, the
install folder needs to be deleted manually.
* Some cleanup along the way... sorry.

forgot these files as part of the previous commit


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@36021 a95241bf-73f2-0310-859d-f6bbb57e9c96