Use ConvertLegacyConfig to check for -32000 pos

It was still possible in 0.3.21 to see (-32000, -32000) window positions under certain circumstances (issue #135). Solve this by using the ConvertLegacyConfig method to interpret -32000 values in config files from <= 0.3.21 as default. This should reset the window positions for anybody who experienced issue #135 once they update to the new version.

Also restore main window position properly even if StartMinimized is enabled.

Unfortunately while doing this I discovered that the Version number isn't loaded correctly (see #135). Have a look at that before merging and let me know if you want to fix this properly first.