Add a new option to Platform::LoadImage to install the image

This change introduce 3 different working mode for Platform::LoadImage
depending on the file specs specified.
* If only a remote file is specified then the remote file is loaded on
  the target (same behavior as before)
* If only a local file is specified then the local file is installed to
  the current working directory and then loaded from there.
* If both local and remote file is specified then the local file is
  installed to the specified location and then loaded from there.

The same options are exposed on the SB API with a new method LoadImage
method while the old signature presers its meaning.

On the command line the installation of the shared library can be specified
with the "--install" option of "process load".

Differential revision: http://reviews.llvm.org/D15152

llvm-svn: 255014