Added .gitignore
Overhauled smart app developers guide anatomy and preferences sections.
Missing images.
Merge remote-tracking branch 'upstream/master'

Conflicts:
	smartapp-developers-guide/preferences-and-settings.rst
SmartApp dev guide updates
a few updates to Bob's doc changes.
Merge pull request #29 from SmartThingsCommunity/review-florian-changes

doc updates to SmartApp developer's guide