CRUD operations for Posts

- added all CRUD operations for Post model
- add() also creates POST_BY_MEMBER and POST_FROM_NETWORK edges
- delete() also deletes associated edges
- delete() currently does not reallocate node/edge indices after deleting
- will write the data to the db.json file and global.db.nodes

server/db/model/edge.js

@@ -1,13 +1,21 @@
 export default class Edge {
-    add(n) {
+    splitEdge(n) {
         let toPrefix = n.to.split("-")[0]
         let fromPrefix = n.from.split("-")[0]
         let type = n.type
-        let prefix = `${fromPrefix}_${type}_${toPrefix}`
+        return `${fromPrefix}_${type}_${toPrefix}`
+    }
 
+    add(n) {
+        let prefix = this.splitEdge(n)
         global.db.addEdge(prefix, n)
     }
 
+    delete(n) {
+        let prefix = this.splitEdge(n)
+        global.db.deleteEdge(prefix, n.from.split("-")[1])
+    }
+
     getByFrom(fromID) {
         let result = []
         for(let i = 0; i < this.entries.length; i++) {