We need to reorganize installer.dll project for a few reasons:
   -We need to move installer.dll src to the install src tree. It's currently in the make tree and the build team has asked us to move it
   -The upcoming MSI redesign project has a new installer.exe that needs some functionality from the installer.dll code for InstallJava() and UninstallJava() functions (but it doesn't need the MSI stuff). This CR will involve moving those particular functions to a shared RegInstallShared.cpp/.h. We will need to continue building installer.dll for use by the JDK installer, and it will be a while before the MSI redesign is pushed. This move will help us keep that project in sync with the JDK8 tree.