message: refactor Put->Post for create routes
diff: import {
  - Authorized, Body, Delete, Get, JsonController, NotFoundError, Param, Put,
  + Authorized, Body, Delete, Get, JsonController, NotFoundError, Param, Post, Put,
  UploadedFile
  } from 'routing-controllers';
  import {Directory} from '../models/mediaManager/Directory';
  @@ -50,13 +50,13 @@ export class MediaController {
  }
  @Authorized(['teacher', 'admin'])
  - @Put('/directory')
  + @Post('/directory')
  async createRootDirectory(@Body() directory: IDirectory) {
  const savedDirectory = await new Directory(directory).save();
  return savedDirectory.toObject();
  }
  @Authorized(['teacher', 'admin'])
  - @Put('/directory/:parent')
  + @Post('/directory/:parent')
  async createDirectory(@Param('parent') parentDirectoryId: string, @Body() directory: IDirectory) {
  const savedDirectory = await new Directory(directory).save();
  @@ -68,7 +68,7 @@ export class MediaController {
  }
  @Authorized(['teacher', 'admin'])
  - @Put('/file/:parent')
  + @Post('/file/:parent')
  async createFile(@Param('parent') parentDirectoryId: string, @UploadedFile('file', {options: uploadOptions}) uploadedFile: any) {
  const file: IFile = new File({
  name: uploadedFile.originalname,
  