Fixes to win32 installation

Added local_internal_options.conf to the installation process. This
file will not be overwritten when an upgrade occurs so changes to how
the agent runs can be made in this file and persist through upgrades.
This fixes #169.

Also, some small fixes like removing whitespace and making the message
box definitions in ossec-installer.nsi a bit more readable.
Merge pull request #179 from awiddersheim/fix_win32_local_internal_conf

Fixes to win32 installation