Bug fixes to Invoke-ReflectivePEInjection

Fixed a bug where calling GetProcAddress by ordinal instead of procedure
name failed.
Fixed a bug where reflectively loading an EXE will cause the entry
function (main()) to be called twice instead of once as expected.
Added a ForceASLR flag to force ASLR to be used even if the PE file
doesn't officially support ASLR.
Some minor other changes.