File Manager: General improvements and bugfixes

[tomas-nestorovic]

This topic includes everything around current implementation of the File Manager. This, however, excludes any modifications tailored for a particular DOS - these should be committed in their own issues. The general modifications of the File Manager should include all of these improvements:

• creation of a mechanism to allow user to choose which columns they want to see, hiding all the others,
• creation of a directory tree, ideally dockable on either on the left (default as in Explorer) or on the right, or hidden altogether,
• information on current selection should be shown in the status-bar (e.g. at least the count of items selected),
• history of folder browsing for current session (like in a web browser, possibility to "go back" and "go forth"),
• the Backspace key should correspond to going to the immediate parent folder (if any, e.g. root directory); this should, in general, be a different action from the above "going back" like in a web browser,
• items that are to be cut should be marked, e.g. with brighter text color like in Explorer,
• ✓ there should be a context menu for each item, allowing common actions like copying, cutting, pasting into, but also actions like displaying the underlying directory entry, or navigating to the first sector of the file,
• if there are any issues with the directory (e.g. some of its sectors are not found, or are marked as bad, or are read with error), the status-bar should indicate such condition in red color,
• file search, including wild chars, e.g. "*.jpg" etc.,
• ✓ the Insert key toggles the selection status for the currently focused file and moves the focus to the immediatelly following file (if any),
• implementation of simple breadcrumbs (e.g. using the SysLink control).
• color the background of "File name" and "Extension" columns with light gray as in many file-handling applications, e.g. WinRar