Allow Page editor to write HTML directly (#1915)

* Works on #1493 
* Adds a new column for Pages to specify format
* Separate out `build_html` into `build_html` and `build_markdown`
* Add config variables into pages: `ctf_name`, `ctf_description`, `ctf_start`, `ctf_end`, `ctf_freeze`
  * The time variables are represented as ISO8601 timestamps

migrations/versions/07dfbe5e1edc_add_format_to_pages.py

@@ -0,0 +1,28 @@
+"""Add format to Pages
+
+Revision ID: 07dfbe5e1edc
+Revises: 75e8ab9a0014
+Create Date: 2021-06-15 19:57:37.410152
+
+"""
+from alembic import op
+import sqlalchemy as sa
+
+
+# revision identifiers, used by Alembic.
+revision = "07dfbe5e1edc"
+down_revision = "75e8ab9a0014"
+branch_labels = None
+depends_on = None
+
+
+def upgrade():
+    # ### commands auto generated by Alembic - please adjust! ###
+    op.add_column("pages", sa.Column("format", sa.String(length=80), nullable=True))
+    # ### end Alembic commands ###
+
+
+def downgrade():
+    # ### commands auto generated by Alembic - please adjust! ###
+    op.drop_column("pages", "format")
+    # ### end Alembic commands ###