Fix #71 study lifetime 7 days.

- this is a hard one to test, but doable if we really want to.
- secondary cleanup by update path in the AddonUpdater (to eventual version 99, depends on Gregg and Ilana)
- 7 days currenlty, hard-set
default message added (fixes #68)
some notification design tweaking
notification design tweaking
added package.json info
addon icon added (fixes #61)
README.md updated (in relation to #66)
Fix #84, rm xpi.  add gitignores.
Merge pull request #84 from gregglind/b84-gitignores

gitignores, rm xpi from tree.
reasons const added
Merge pull request #78 from gregglind/b78-makefile

makefile to make experiment
Merge branch 'master' of github.com:raymak/contextualfeaturerecommender
conflict resolved
selfuninstaller merge
Fix #78, makefile