Tweak `en-*`

* removes some ambiguity between authors, users and commenters.
* `hrs/days ago` &rarr; `hours/days ago`
* tidy `install_langfile` URL
* downplay the newness on `new_textpattern_version_available`;
pedantically, it won’t be completely new
* tense on `problem_connecting_rpc_server`
* terminology on `comment_recorded`
* sentence structure on `deprecated_configuration`
* `enter_comment_here` is less clumsy
*  code block on `missing_article_tag`
* typo on `plugin_load_error`
* `press_preview_then_submit` is less emotive
* switch database related stuff to MySQL terms (`user name` rather than
`login`)
* `please_enter_url` doesn’t _have_ to be web-reachable (hi, localhost
and intranets)
* `set_temp_dir_prefs` now refers to Textpattern and not the shadowy
cabal `we`
* `tag_email` spam-proof email is not ever going to happen, so wording
changed a little