v2.51, ladder customisation & layout

[Gavin]

v2.51.0.0. Released 8/2/2013.

Ladder changes:
- Ladder layouts are now saved to file so you can saved unlimited layouts for different trading scenarios / styles.
- Ladder column widths are now also saved when you save the layout.
- Panel sizes are also now saved when you saved the layout.
- Default layout file is also shown in the main window's settings pages (accessed form the File menu).
More ladder customisations:
- Edit and save the values of preset stake buttons
- Hide the preset stake buttons

Chart changes:
- You can now save the layout as default so that it loads automatically when you open a chart. So you no longer need to keep choosing your layout file.
- Default layout file is also shown in the main window's settings pages (accessed form the File menu).