This is covered by the Media Library and the Insert/Edit Image button in the WYSIWYG editor.
Uploading: In Media Library, click the Upload button. Alternatively, open the Media Library via the Insert/Edit Image button in the WYSIWYG editor.
Renaming: In Media Library, click the pencil icon next to the file. This may break pages that reference the file under the old name (obviously).
Moving: Not officially supported by Media Library. Right now, it works because the Rename functionality allows for the use of '/' and '.', so you can do things like renaming to '../../otherfolder/newname'. This will (hopefully) be removed in the future. I do not feel a large need for moving files, as you can simply download them and upload them at a different location. If you wish to move many files, we can always do so for you at the filesystem level.
Deleting In Media Library, click the trash icon next to the file. This may break pages that reference the file (obviously).
Resizing: the menu under the Insert/Edit Image button in the WYSIWYG editor has a field 'Dimensions' under the tab 'Appearance'. Filling these out leads to a true resize of the picture.
For use in blog posts, static pages and events. Should include resizing to the proper size.