Merge pull request #66 from michalbe/haida-content

sheet duplication restored
Caching the screenshots.
The current invalidation heuristic is to throw the screenshot away if
the sheet is displayed for more than 1.5sec.
Merge pull request #68 from etiennesegonzac/screenshot-caching

Caching the screenshots.
Merge pull request #69 from michalbe/haida-content

cleaning
Make error handling more robust
Merge branch 'content' of github.com:vingtetun/gaia into HEAD
Merge pull request #70 from michalbe/haida-content

sms links in new sheet
fix access to developer tool
Merge pull request #71 from samjoch/content-settings

fix access to developer tool
fix display panel
Merge pull request #72 from samjoch/content-settings

fix display panel
1st step of making contacts sheetable :)