Bug 838223 - lazy script loading and DB enumeration changes for faster startup

load photo/video view scripts on demand

don't load gesture detector until we need it

don't load metadata parsing code unless needed

get rid of spinner on startup

move WebGL shaders from html file to ImageEditor.js

change the db enumeration algorithm for faster startup

fix strict mode for ImageEditor.js
Merge pull request #8054 from davidflanagan/bug838223

Bug 838223 - lazy script loading and DB enumeration changes for faster startup