[feature] New Preference setting : Use case-insensitive sorting in lists

[goran-w]

Whether to sort lists using case-sensitive or case-insensitive ordering is a (usually strong) matter of taste and conventions.

To satisfy both camps, this option can now be toggled as a (global) Preferences checkbox (on the Appearance tab). When toggling this option, a RefreshAll() is performed to directly update visible lists.

NOTE: This also affects the non-digit substrings in NumericSort.Compare(). Additionally, that method is now refactored to remove some redunant code.

Fixed a missing case of numeric sorting, for root items in the RevisionFileTreeNode tree (which were still using ordinal string.Compare() instead of the intended NumericSort.Compare()). This is related to issue #597 and commit 76a7a22 which added "numeric sorting for all trees". The issue is corrected by refactoring the node sorting into a separate method, to make sure sorting is done the same way in both of the call-sites.

To support sorting options in Local Changes (Unstaged / Staged) lists, the output list from QueryLocalChanges() is now sorted by Path (instead of relying "blindly" on the sorting done by Git). Also, WorkingCopy.IsChanged() is now simplified / optimized and will additionally react to changes in sorting order.

[goran-w]

@love-linger would you consider merging this PR? It's a bit frustrating to switch between SourceGit and other tools (like Windows Explorer 😬) that ignore case when sorting files... (SourceGit does a special "numerical sorting", for only certain lists, but does not support the much more basic sorting-option of optionally ignoring case.)

Personally, I find it harder to locate names in case-sensitive lists. For example, in the list below, bee is not located between Beat and Bell - I have to look through two "sections" of the list to find it...

Art
Beat
Bell
Boo
Cow
Deep
Early
Far
arty
bee
cee
dee
fee

(BTW, there's additionally a bug-fix for numerical sorting of root RevisionFileTreeNode items in the first commit of this PR.)

[love-linger]

I've pushed a commit that use case-insensitive sorting in all filesystem related trees/lists by default. I do not want to add too many configurations.

[goran-w]

@love-linger Thanks! However, I just realized that Commit.ParseDecorators() should also use the (case-insensitive) NumericSort.Compare() method, when comparing names for decorators (of same Type) in the call to Decorators.Sort(), since that's how Branches and Tags are sorted elsewhere...

[love-linger]

Done