app install on sdcard. provide skeleton implementation

to install an app on sdcard, just resources.
Add new install path for /asec in installd.
ignore . when checking for apk path since the sdcard packages id'ed
by package name.
Add new -s option to adb shell pm
Refactor fwd locked from scanMode to ApplicationInfo.
Add new flag for sd install
Add new parse flags for fwd locking and installing on sdcard
New mock api's in PackageManagerService to invoke MountService api's. These
will be refactored again and so have been wrapped internally.
Some error codes in PackageManager
Changes in PackageManagerService to use mPath and mScanPath during installation
and switch to using PackageParser.Package.applicationInfo attributes for
source and public resource directories.
Some known issues that will be addressed later
 using system_uid for now. needs some tinkering with uid and packagesetting creation to use the actual app uid
 error handling from vold not very robust. ignoring lot of things for now
 sending a delayed destroy to delete packages. will revisit later
 revisit temp file creation later. just copy for now