readme updates
Removed Controller\Admin

currently not used
uninstall() updated
Settings page updated

How to get Client id and secret explaind
view image button added to imgur upload form

button is shown when image is attched to ticket
imgur secrect token is not required when saving config
imageExists client api call added which returns url string or false
corrected mistype
setting page updated

Added description how to use extension
removed copy paste unrelated code