kcms/webshortcuts: make labels more consistent

When adding a new entry or modifying an existing one, the terminology switches from "Web search keywords" (used in the main dialog and e.g. in the Plasma Search kcm, to "shortcut". The button for altering an existing Web search keyword is labeled "Change", but the corresponding dialog is titled "Modify [...]"; neither of them is the commonly used term for editing entries in a listview, "Edit" (used, for example, in the kwin rules, keyboard shortcut, or file association kcms). Most, but not all instances of Web are capitalized. The add/modify dialog contains the somewhat opaque term "charset". Finally, the HIG recommend using a unicode ellipsis character "…" instead of three dots, but the "New..." and "Change..." buttons still have individual dots.

This change modifies the New/Edit dialog labels to be consistent with the ones in the main kcm (including not using the term "shortcut" and matching button labels as well as column headers used there), labels the button in the main kcm "Edit", capitalizes "Web" consistently (style guides vary, but the HIG explicitly recommends capitalization for "Internet" so capitalizing "Web" seems to be in the spirit of the guidelines), de-abbreviates "Character set", and substitutes ellipsis characters where appropriate.

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