Separate split and merge menu items and icons

Separate split and merge menu items and icons.
Collapse reason & process group in readonly mode

Collapse the reason & process group in readonly mode.
Use different method so that converters aren't used

Use different method so that converters aren't used by returning a
System.Windows.Visibility value instead of a bool that then needs
converting.
Enable copy from Incid textbox

Enable copy from Incid textbox by setting Enabled=true and
IsReadOnly=True and then adding a template trigger to make the Textboxes
of these types appear disabled.
Draft changes to theme to improve contrast

Draft changes to theme to improve contrast.
Tweak colours and set some comboboxes as readonly

Tweak colours and set some comboboxes that should already be as
readonly.
Added menu option to switch theme

Added menu option to switch theme dynamically.
Added new dark theme - draft

Added new dark theme - draft.
Amended dark theme style

Amended dark theme style.
Added ability to save and retrieve default colour

Added ability to save and retrieve default colour from user settings.
New & amended style themes

New & amended style themes.
Tweak to opacity of disabled icons

Tweak to opacity of disabled icons.
Adjusted left margin on editable comboboxes

Adjusted left margin on editable comboboxes.
Fix exception when first loading main form

Fix exception when first loading main form.
Remove hard-coded resource themes

Remove hard-coded resource themes.
Tweaks to light and dark grey themes

Tweaks to light and dark grey themes.
Various tweaks to get application to build

Various tweaks to get application to build.
Remove unused themes

Remove unused themes.
Adjust appearance of themes

Adjust appearance of themes.
Only enable logical split menu/button when valid

Only enable logical split menu/button if a subset of all the features
for the current incid have been selected.