Cleanup 'defcustom' types and docstrings

Cleanup 'defcustom' types and docstrings

* sweeprolog.el (sweeprolog-swipl-sources)
(sweeprolog-module-header-comment-skeleton)
(sweeprolog-indent-offset, sweeprolog-qq-mode-alist)
(sweeprolog-enable-cycle-spacing)
(sweeprolog-analyze-buffer-on-idle)
(sweeprolog-analyze-buffer-max-size)
(sweeprolog-analyze-buffer-min-interval)
(sweeprolog-swipl-path)
(sweeprolog-messages-buffer-name)
(sweeprolog-read-flag-prompt)
(sweeprolog-read-module-prompt)
(sweeprolog-read-predicate-prompt)
(sweeprolog-read-exportable-predicate-prompt)
(sweeprolog-read-pack-prompt)
(sweeprolog-top-level-display-action)
(sweeprolog-top-level-min-history-length)
(sweeprolog-init-args)
(sweeprolog-enable-flymake)
(sweeprolog-note-implicit-autoloads)
(sweeprolog-enable-eldoc)
(sweeprolog-enable-cursor-sensor)
(sweeprolog-new-predicate-location-function)
(sweeprolog-top-level-signal-default-goal)
(sweeprolog-highlight-holes)
(sweeprolog-read-predicate-documentation-function)
(sweeprolog-enable-help-echo)
(sweeprolog-rename-variable-allow-existing)
(sweeprolog-dependency-directive)
(sweeprolog-highlight-breakpoints)
(sweeprolog-top-level-persistent-history): Minor docstring and ':type'
touch ups.
(sweeprolog-init-on-load): Remove obsolete option.
(sweeprolog-libswipl-path): Remove unused option.
(sweeprolog-menu)
(sweeprolog-start-prolog-server)
(sweeprolog-message)
(sweeprolog-top-level-menu-kill)
(sweeprolog-top-level-menu-go-to)
(sweeprolog-top-level-menu-mode): Minor docstring improvements.
(sweeprolog-submit-bug-report): Stop including
'sweeprolog-libswipl-path' in bug reports.