rewrite the project as a static site generator

this removes Flask, reworks a number of library methods accordingly, and
adds generators and build commands to process the instance directory
(largely unchanged, except config.py is now config.json) and spit out
files suitable to be served by a web server such as Nginx.

there are probably some rough edges here, but overall this works.

also note, as this is no longer server software on a network, the
license has changed from AGPLv3 to GPLv3, and the "or any later version"
allowance has been removed

Signed-off-by: Brian S. Stephan <bss@incorporeal.org>

incorporealcms/mdx/figures.py

@@ -1,10 +1,10 @@
 """Create generic figures with captions.
 
 SPDX-FileCopyrightText: © 2022 Brian S. Stephan <bss@incorporeal.org>
-SPDX-License-Identifier: AGPL-3.0-or-later
+SPDX-License-Identifier: GPL-3.0-only
 """
 import re
-from xml.etree.ElementTree import SubElement  # nosec B405 - not parsing untrusted XML here
+from xml.etree.ElementTree import SubElement  # nosec B405
 
 import markdown