Makes [summary] independant from [truncate] variable

[brunogeronimo]

As a post can also have a custom summary, it might make more sense to have a separated condition to show/hide a post summary from the page.

[lomion0815]

I would support merging that PR. Additionally use plainify on summary in order to not have formated text (e.g. bold words) in the summary.

[matsuyoshi30]

@brunogeronimo Hi! Thanks for your contribution and sorry for late my response... Could you resolve conflict, and contribute again? Thanks!