Find cmder files when running as Administrator.

When starting a shell as Administrator, the CMDER_ROOT variable is
not propagated from the parent (non-Admin) environment.
Fix this by using paths relative to %ConEmuDir%.

Fixes issue #94.
Remove extraneous quotes.

Extra quotes in previous commit caused PATH to be set incorrectly in admin
shell.
Merge pull request #166 from glucas/run_as_admin

Find cmder files when running as Administrator.