Gnc-Prefs: update the windows build system to handle gsettings properly

- drop installation of files in libexec (we don't ship any anymore)
- make sure gsettings schema files get installed
- drop ORBit2; this was a requirement for GConf only

git-svn-id: svn+ssh://svn.gnucash.org/repo/gnucash/trunk@23270 57a11ea4-9604-0410-9ed3-97b8803252fd
Gnc-Prefs: add convenience functions for int64 and coords typed preferences

coords are a pair of floats

git-svn-id: svn+ssh://svn.gnucash.org/repo/gnucash/trunk@23271 57a11ea4-9604-0410-9ed3-97b8803252fd