Formatted image file data structure that breaks down by subdir (#1102)

- New utility method for the web app, which sorts image files into dicts where the subdir is the key
- In the web ui, display each subdir in a table nested in a details tag.
- Allow for picking destination subdir when uploading files
- Style the expandable details blocks in the images table
- Add a check for ~ paths to the is_safe_path() utility method

python/web/src/static/themes/classic/style.css

@@ -104,6 +104,15 @@ ul.inline_list {
   list-style: none;
 }
 
+summary.dirname {
+  text-decoration: underline;
+  font-family: monospace;
+}
+
+summary.filename {
+  text-decoration: underline;
+}
+
 .dropzone, .dropzone * {
   box-sizing: border-box;
 }

python/web/src/static/themes/modern/style.css

@@ -53,7 +53,7 @@ input[type="radio"] {
   margin: 0 0.1rem 0 0.75rem;
 }
 
-div.noscriptmsg {
+div.notice {
   background: var(--danger);
   border-radius: var(--border-radius);
   padding: 0.5rem;
@@ -717,6 +717,16 @@ section#files p {
   margin-top: 1rem;
 }
 
+section#files details.subdir summary.dirname {
+  text-decoration: underline;
+  font-family: monospace;
+  margin: 0.5rem 0;
+}
+
+section#files details.contents summary.filename {
+  text-decoration: underline;
+}
+
 @media (max-width: 900px) {
   section#files table#images tr th:nth-child(2),
   section#files table#images tr td:nth-child(2) {