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.
Restore window pos even if start minimized
Merge pull request #144 from dvide/convert-v0.3.21-config

Use ConvertLegacyConfig to check for -32000 pos
fixed version initialization
Positions of additional windows are NaN, if never opened.  Resulting in positions being saved as int.MinValue.
fixed an issue where "import from file" would for some reason call "ListViewDB_MouseLeftButtonUp"