Revert from emacsql-sqlite3 to emacsql-sqlite for foreign key support.
This makes it slightly harder to get Org-roam up and running for
Windows, but not impossible, but foreign keys makes database operations
faster and keeps the code clean.
Also, fix schemata for foreign keys on various tables, and add indices
where joins are common (org-roam-db--table-indices).
Add 2 custom handlers:
1. roam-file?file=path: this simply opens the file at path in Emacs.
2. roam-ref?ref=ref&template=roam-template&title=title&...: attempts to open a roam note with a given ROAM_KEY. If the note doesn't exist, create one. Else, open it.
All org-roam related information will now be stored in the database. Henceforth, the cache needs to be built synchronously once (via `M-x org-roam-build-cache`), which is then incrementally updated.
Each org-roam-directory gets its own cache. One can override the `org-roam-directory` variable locally via dir-locals:
((org-mode . ((eval . (setq-local org-roam-directory (expand-file-name "./"))))))
* fix org-roam--parse-content incorrect :to computation
org-roam--parse-content always computed the to-path relative to the
org-roam-directory, when it should be relative to the file-path in
question. Fixes#81.
* Add to changelog
