r8256: - allow rpc calls from non-command line ejs contexts by creating a set

r8256: - allow rpc calls from non-command line ejs contexts by creating a set
  of null credentials to use if cmdline_credentials is not setup

- hide the length and size elements of a lsa_String from js scripts,
  so you can use a lsa_String just as an ordinary string without
  knowing its a structure. We won't do this with all structures, just
  a few core ones that are used often enough to warrant it.

- make sure returned ldb arrays have a length property
(This used to be commit 12d2092dd8668de41776132ccbcd634790c371a9)