6ux installer should register/unregister deploy toolkit plugin for FF/Chrome properly

The jre 6 installer just copies the deploy toolkit plugin (npDeployJava1.dll) for FF/Chrome into the {jre_home}/bin/new_plugin director and doesn't register it in the registry. FF/Chrome is able to find it by chance because when it tries to load the java plugin (npjp2.dll), it also loads the npDeployJava1.dll since they're in the same directory and the filename also starts with "np". This is problematic for Chrome - see 7084647 for details.

To address this problem, jre 6 installer should perform the following:

On installation:
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1) the installer should copy npDeployJava1.dll into a different directory from where the java plugin (npjp2.dll) is located, e.g. c:\program files\java\jre6\bin\dtplugin

2) Check if the following registry key exists:
[HKEY_LOCAL_MACHINE\SOFTWARE\MozillaPlugins\@java.com/DTPlugin]
   a) if it exists, check if the version of the file pointed to by the "Path" subkey
      is newer than the one currently being installed. If yes, do nothing since a
      newer version of npDeployJava1.dll was registered.
      If no, remove the existing keys with the "@java.com/DTPlugin" prefix and create
      a registry entry as mentioned in step b.
   b) if it doesn't exist, create the following registry key:
      [HKEY_LOCAL_MACHINE\SOFTWARE\MozillaPlugins\@java.com/DTPlugin]
       "Path"="C:\\Program files\\java\\jre6\\bin\\dtplugin\\npDeployJava1.dll"

On Uninstallation:
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Check if the currently registered npDeployJava1.dll is newer.
If yes, do nothing.
If no, do the following:
copy the npDeployJava1.dll from the dtplugin directory into the system32 directory.
remove all subkeys with "@java.com/DTPlugin" under HKEY_LOCAL_MACHINE\SOFTWARE\MozillaPlugins.
register the npDeployJava1.dll in the system32 directory as in step 1b above.