Slighty smarter rebuild on page content change

Add global get_page tera fn

Sections

Useful if you're creating a section only to access it in the index but
do not want a section page for it

Pagination

Fix #53

Allow sorting pages by order and date

Closes #14, #43

Fix #51

Index page

Avoid issues with temp files from some editors

Add more sublime syntaxes

The packdumps contains the fixed Linker syntax too so it can be
used

Also fix gutenberg serve that has been broken (not
re-rendering content) for quite some time now.

Add missing fields to serialization

Also use Option for Page::summary

Close #38

Copy only static files that triggered the change notification