add a new CollectionViewCell type - Aside type
如果是旁白类型显示格式，则在多媒体数据上不附件任何Mask
在aside模式下，图片可以根据原始比例显示，并且宽度撑满父容器
verify outlets. close #604
expose cache countLimit. set default to 200. ref: #492
fix toolbar constraints and correctly size send button to fit text. close #603
adjust input toolbar layout and button sizes.
Merge remote-tracking branch 'upstream/develop' into develop