Fix #1060 -- add `nikola new_page`

Signed-off-by: Chris “Kwpolska” Warrick <kwpolska@gmail.com>
add the is_post parameter for create_post

Signed-off-by: Chris “Kwpolska” Warrick <kwpolska@gmail.com>
Changelog entry for new_page

[ci skip]

Signed-off-by: Chris “Kwpolska” Warrick <kwpolska@gmail.com>
Merge pull request #1077 from getnikola/new_page

Add `nikola new_page`