Add support for hashtag on user interface

Add migration to fix typo
Add support for linking hashtags with posts
Rework tag search page so it says a nicer message than page not found
when no post use that tag
Add new string to translation

migrations/postgres/2018-10-20-164036_fix_hastag_typo/down.sql

@@ -0,0 +1,2 @@
+-- This file should undo anything in `up.sql`
+ALTER TABLE tags RENAME COLUMN is_hashtag TO is_hastag;

migrations/postgres/2018-10-20-164036_fix_hastag_typo/up.sql

@@ -0,0 +1 @@
+ALTER TABLE tags RENAME COLUMN is_hastag TO is_hashtag;

migrations/sqlite/2018-10-20-164036_fix_hastag_typo/down.sql

@@ -0,0 +1,10 @@
+CREATE TABLE tags2 (
+    id INTEGER NOT NULL PRIMARY KEY AUTOINCREMENT,
+    tag TEXT NOT NULL DEFAULT '',
+    is_hastag BOOLEAN NOT NULL DEFAULT 'f',
+    post_id INTEGER REFERENCES posts(id) ON DELETE CASCADE NOT NULL
+);
+
+INSERT INTO tags2 SELECT * FROM tags;
+DROP TABLE tags;
+ALTER TABLE tags2 RENAME TO tags;

migrations/sqlite/2018-10-20-164036_fix_hastag_typo/up.sql

@@ -0,0 +1,10 @@
+CREATE TABLE tags2 (
+    id INTEGER NOT NULL PRIMARY KEY AUTOINCREMENT,
+    tag TEXT NOT NULL DEFAULT '',
+    is_hashtag BOOLEAN NOT NULL DEFAULT 'f',
+    post_id INTEGER REFERENCES posts(id) ON DELETE CASCADE NOT NULL
+);
+
+INSERT INTO tags2 SELECT * FROM tags;
+DROP TABLE tags;
+ALTER TABLE tags2 RENAME TO tags;