core: cleanup in RunVmParams

1. Rename methods & fields that had '_' in the middle of their name
   to the standard convention in Java
2. Remove the '_' and "private" prefixes from several class fields
3. Remove unused and redundant constructors

Change-Id: Iebc0d1a33b991e444f0639978bb08ccd5eade350
Signed-off-by: Arik Hadas <ahadas@redhat.com>