Remove hardcoded "Preferences" strings in c/b/extensions

And cleaned up other hardcoded strings on the fly as I noticed them.

BUG=343692

Review URL: https://codereview.chromium.org/162813005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@251559 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 251559
Add the it2me native messaging host to the windows installer.

BUG=338952

Review URL: https://codereview.chromium.org/168113002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@251560 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 251560