[SHELL32] brsfolder.cpp: Refactoring

Modernize source code. Improve readability and reduce confusing.
JIRA issue: CORE-17340
- Rename browse_info as BrsFolder.
- Rename TV_ITEMDATA as BrsItemData.
- Rename InsertTreeViewItem as BrsFolder_InsertItem.
- Rename InitializeTreeView as BrsFolder_InitTreeView.
- Rename GetIcon as BrsFolder_GetIcon.
- Rename GetNormalAndSelectedIcons as BrsFolder_GetIconPair.
- Rename GetName as BrsFolder_GetName.
- Fix some confusing and/or non-standard variable names.
- Use ATL to simplify logics.