Add page template

Category and tags defined in pages do not appear in the categories and
tags variable so there is no point is displaying them.
Set copyright meta tag to author name instead of site license
Properly close meta tags
Set keyword meta tags for article and pages
Do not show comments on Page
Make path of search.html absolute in search form action

search.html is always at root so its path should be absolute.

Thanks to @if1live for pointing it out.

https://github.com/if1live/pelican-elegant/commit/3da52903e94051fa771212149a10a271adc78264#commitcomment-3988674

> my pelicanconf.py is..
>
> ```
> ARTICLE_URL = 'posts/{slug}/'
> ARTICLE_SAVE_AS = 'posts/{slug}/index.html'
> ```
>
> what is problem?
> 1. goto article page. current url : /posts/some-article/
> 2. search. current url : /posts/some-article/search.html?... but search.html is in root path.
>
> search.html is always in root path. so you can use absoulte path.
Validate search form of 404 page

I missed to add validate check for it when I added it for the main menu
Update Release notes
Add Thanks file to the repository