Do not apply sanitization to root path when generating paths for downloaded assets in the cache folder

[fthevenet]

This PR aims to address issue #972

Application launched via a JNLP file will failed to start for user wtih certain characters in their home folder (e.g. C:\Users\Foo_O'Bar), which is a legal path on Windows, but paths for downloaded asset are incorrectly sanitize as C:\Users\Foo_O_Bar and the application then fails as it attempts to access content in C:\Users\Foo_O_Bar\... instead of C:\Users\Foo_OBar...