Document usage of both portable settings.ini and non portable %ProgramData%\TheForceEngine

[lwcorp]

Thanks for making this launcher portable in #364!

However, https://theforceengine.github.io/Documentation.html states:

Note that TFE stores saves, set up info, screenshots, log files, and similar items under Documents/TheForceEngine/. A portable installation option, where all data is kept in the local directory, is planned for the future.

Yet that's not actually true, as:

1. By default it also creates %ProgramData%\TheForceEngine
2. If one manually creates an empty settings.ini inside the launcher's own folder, it stores everything in files and subfolders under the launcher's own folder.

For the former, I believe the culprit is TheForceEngine/TFE_FileSystem/paths.cpp which uses both CSIDL_MYDOCUMENTS and CSIDL_COMMON_APPDATA. It also checks for settings.ini via bool isPortableInstall().

But this is just a request to document that:

1. By default it uses ProgramData\TheForceEngine\ and not just Documents\TheForceEngine\.
2. One can create a blank settings.ini to avoid all that.